A boat is said to be turtling or to turn turtle when it is fully inverted.^[1][2] The name stems from the appearance of the upside-down boat, similar to the carapace (top shell) of a sea turtle.^[3][A][B] The term can be applied to any vessel; turning turtle is less frequent but more dangerous on ships than on smaller boats.^[C][4] It is rarer but more hazardous for multihulls than for monohulls, because multihulls are harder to flip in both directions. Measures can be taken to prevent a capsize (where the boat is knocked over on its beam-ends but not yet inverted) from becoming a turtle (with bottom up).^[5][6][7][8]

When a boat is "turned over completely" it has turned turtle.^[1][2][3][9] Some sources treat the term "turtle" as synonymous with "capsize" or "keel over".^[4][10] but most others make a distinction.^[D] Carrying too much sail or loss of control can lead to broaching—the boat heels too far to one side, or capsizes.^[11] While all turtlings involve a capsize, the converse is untrue. Prevention is the first priority.^{[6][7] [E]}

With the exception of self-righting watercraft, vessels have an angle of vanishing stability (AVS). External forces aside, if they are tilted at an angle less than the AVS, they will pop back upright. If they are tilted at an angle greater than the AVS, they will turn turtle and stay there. In other words, non-self-righting vessels are stable when turtled. Their primary stability and secondary stability are greater than zero, tending to right them, but their tertiary or inverted stability is less than zero, and tends to keep them upside-down.^[12]

Capsizing (but not necessarily turtling) is an inherent part of dinghy sailing, and is considered to be "routine". It is not a question of "if" but a question of "when".^[8][13][14]

For those who prefer to avoid the experience, a keelboat monohull has physics on its side.^[13][15] (See limit of positive stability.) But even yachts can capsize and turtle in extraordinary conditions, so design considerations and suitability for particular tasks, locations, weather, duration and situations are essential queries.^{[13][14][15][16][17][18][19][20]} "Such events can overcome skill and experience"; boats need to be appropriate for foreseeable conditions.^{[14][15][16][17][19][21]} It is a fundamental question of seaworthiness.

Turtling commonly occurs when a boat capsizes and is not righted or attended to in time, allowing it to roll through the approximately 90 degrees of a capsize through to 180 degrees from upright.^[6][7]

Prevention and delay of turtling in dinghies is the highest priority^[20]—turtling can be catastrophic in consequences—but it depends on skill, ability and athleticism, which vary greatly.^[8][20] As John Rousmaniere wrote: Testing confirms the Royal Yachting Association's conclusion that "a decisive way to address entrapment is to immediately right the boat by putting weight on the centerboard", daggerboard, (or bilgeboard in a scow).^[6] His 2012 report advises that "US Sailing and other organizations should consider establishing this as doctrine." Thus, reliance on boat handling and seamanship may be misplaced.^[6]

Sealing masts and attaching flotation are effective preventatives for turtling of dinghies, but not widely utilized.^[6][7] More certain preventatives for this includes various forms of flotation added to the tip of the mast or top of the mainsail.^[F] These include floats (e.g., one that looks like a streamlined blimp used on Hobie 16s)^[G][22] or a "sail patch"—a sleeve with built in flotation that fits over the top of the sail, available for example as option on the Wayfarer (dinghy) Mark IV.^[8][20] Another alternative is to seal the mast, thereby increasing its buoyancy.^[22]

As an emergency palliative, putting flotation (i.e., a spare life vest or other personal flotation device), onto the end of the mast straight away after a capsize and without delay, can forestall a turtle. Conversely, climbing onto the side of a knocked down boat can increase the likelihood of turtling, as it moves weight higher over the center of gravity, may also increase windage, and thus can effectively drive the mast downward.^[7]

Several devices have been patented to prevent turtling.^[23][24] Capsizing is particularly troublesome for catamarans and trimarans, which are especially hard to right.^[6][23]

The use of a trapeze, harness, jackline or other tether can cause injury or death due to entrapment if a boat turtles.^{[6][17][21][25]}

Righting a turtled dinghy is one of the most difficult maneuvers. Recovery in a monohull requires releasing the main sheet and jib sheet, lowering the spinnaker if it is deployed, standing on the bottom of the boat and levering on the centerboard, or standing on the centerboard (there may be weight and placement restrictions). It is important that other members of the crew not be on top the boat, as this can drastically increase resistance to righting the craft.^[7] The use of "righting ropes" materially aids the process. Standing on the centerboard and "piggybacking" of crew members can be highly effective to right a turtled dinghy, as it increases both the weight and leverage being applied. Use of powerboats to aid is problematical, and depending on the technique used—there are several—may or may not succeed.^[6] See Capsize.^[26] Rigging righting lines depends upon proper placement, and critically should be done in advance of the need to use them.^[20][27]

In yacht sailing, multihulls are deemed to be more prone to turtling than keeled monohulls, and there is essentially no way to right them if they overturn. The juxtaposition of the hulls and sail when turtled—it makes them inherently stable when inverted—makes them especially resistant to righting.^[6][23] Consequently, some larger multihulls are built with a turtle emergency escape hatch beneath the hull. Indeed, some locales require such safety hatches.^[28] There are, however, those who feel that the likelihood of a capsize of a large multihull is overrated.^[29][30] There are others who state that a self-righting multihull is the answer, along with designing in safety and proper operation.^[28] A patent has been issued specifically concerning righting of turtled large multihulls.^[31] It is intended to avoid the necessity to use divers and special equipment in a recovery.^[31]

It is, however, possible (and often successfully) to right a capsized small multihull, e.g., a Beachcat and Hobie 16. The process begins with positioning ropes so that the crew can get leverage (acting together is key). Righting Beach catamarans that are turtled can be extremely difficult. Loss of sails, rigging, masts and boats can occur,^[26] not to mention sailors.^[8] A singled-handed self-rescue can be assisted by filling a garbage bag (called in this context a "righting bag") with water, and throwing it over the rescuer's shoulder.^[26] See Hobie 16 which suggests sitting on the rear of one sponson, which will upturn a turtled Hobie.

Even some large multihulls can be righted at sea—it is a long shot—provided that the skipper is well prepared, knows what they are doing, and has appropriate devices, tools, skills, a workable plan, cooperative waves, weather and wind, and some luck.^[28][29]

The Fastnet race, and particularly the 1979 Fastnet race (the disastrous race that changed yacht racing for all time),^[18][32][33] has been the occasion for many sailboat capsizes, turtlings and fatalities.^[18][19] In the 1979 race, "15 sailors died, five boats sank, and at least 75 boats flipped upside down."^[18] In any event, adopting heaving to as a storm tactic proved to be a good preventive of capsize during the race. Not one of the hove to yachts were capsized or suffered any serious damage.^[34] See also Capsize of Drum (1985) and Capsize of Rambler (2011),^[14] both of which involved large Maxi yachts that lost their keels.^[H]

In December 2008, the high speed experimental sailing hydrofoil trimaran Hydroptère set a world speed record, then pitchpoled while going over 60 knots. The turtled yacht had to be towed back to port for being turned right side up.^[35]

In the 2011 Chicago Yacht Club Race to Mackinac, the high performance monohull sportsyacht WingNuts, a Kiwi 35, turtled in an extreme storm, killing the captain and one crew member. Later inquiry determined the boat—specifically its high performance extremely wide low displacement hull^[21][25][36]—was unfit for the location, weather, and the lengthy multiday race format, and urged race officials to change ratings and revoke privileges for similar boats to enter the race.^{[14][16][17][25][I]} The waves were not all that unusual, although the wind was. The boat may have buried one of its hiking wings into a wave, causing it to 'trip', and had the other lifted by the wind.^[36] It is rare but not unheard of for keelboats to turtle and remain upside down, particularly if its keel is intact. However, this boat's unique hull form, which made it very fast, also rendered it more stable upside down than right side up. This was a recipe for the disaster.^[21][36] This loss was occasioned despite a competent and experienced crew which was as well equipped and prepared as thought to be necessary.^{[14][16][17][21][36]} WingNuts met then current offshore stability standards, which failed to adequately take into account the dynamic effect of the "radical" winged hull.^{[14][16][25][36][J]}

On 13 June 2012, in the trials leading to the America's Cup, Oracle Team USA on an AC45 spectacularly capsized the boat, and it was righted with minimal damage ("there's a little rip there") ten minutes later. Skipper Russell Coutts dismissed it as "a learning experience". This was an epilogue to earlier similar incidents by other teams in Australia.^[37][38]

On 9 May 2013, the 2013 America's Cup challenger Artemis broke apart, broached, capsized, and turtled destroying its wing/sail and trapping two crew members under its hull. The AC72 wing-sail catamaran was sailed on behalf of the Royal Swedish Yacht Club, sponsoring Team Artemis. Andrew "Bart" Simpson, an Olympic-gold medal-winning British sailor, died as a result.^[39][40]

Capsize and turtling can result in legal liability for damages due to negligence.^[41]

• A naval encyclopædia: comprising a dictionary of nautical words and phrases; biographical notices, and records of naval officers; special articles of naval art and science. PHILADELPHIA: LR HAMERSLY & CO. 1881. Retrieved 23 January 2014. at Internet Archive
• Colgate, Stephen (1978). Fundamentals of Sailing, Cruising, & Racing. New York: W.W. Norton & Company. pp. 97–100. ISBN 0-393-03811-4.
• Dashew, Steve (8 January 2012). "Evaluating Stability and Capsize Risks for Yachts". setsail.com. Retrieved 22 November 2013.
• Forbes, Sir Hugh; Laing, Sir Maurice; Myatt, Lt. Col. James. "1979 Fastnet Race Inquiry" (PDF). Blur.se. Royal Yachting Association, Royal Ocean Racing Club. Retrieved 3 July 2012.
• "Fusion Capsize Manual" (PDF). F-15 dinghy. Archived from the original (PDF) on 2 December 2013. Retrieved 18 November 2013.
• George, M. B. (22 June 1984). Basic Sailing: A Practical Course in Sailboat Handling. Motor Boating and Sailing Books (First ed.). Hearst Marine. p. 112. ISBN 0688035671. ISBN 978-0688035679
• Hawley, Chuck; Rousmaniere, John; Naranjo, Ralph; McCurdy, Shiela (18 October 2011). "Inquiry into the Chicago yacht Club-Race to Mackinac Capsize and Fatalities". US Sailing. Archived from the original on 11 November 2011. Retrieved 23 November 2011.
• Jobson, Gary (2005). Sailing Fundamentals. New York: Simon & Schuster. pp. 192–194. ISBN 978-0-7432-7308-4.
• Landry, Chris (31 January 2012). "Boat in fatal capsize was 'inappropriate' for race". Soundings. Retrieved 7 December 2013.
• Layton, C.W.T., F.R.A.S., M.R.I.N. Assoc. R.I.N.A.; Clissold, Peter, Commander R.N.R. (Retd.), Master Mariner, Younger Brother of Trinity House, Fellow of the Royal Institute of Navigation revised ; Miller, Captain A. G. W. Extra master revised this edition (1994). "Dictionary of Nautical Words and Terms: 8000 Definitions in Navigation, Seamanship, Rigging, Meteorology, Astronomy, Naval Architecture, Average, Ship Economics, Hydrography, Cargo Stowage, Marine Engineering, Ice Terminology, Buoyage, Yachting, etc" (PDF) (Revised Fourth ed.). Glasgow: Brown, Son & Ferguson, Ltd., Nautical publishers. pp. 71, 370. Archived from the original (PDF) on 27 February 2014. Retrieved 23 February 2014.{{cite web}}: CS1 maint: multiple names: authors list (link)
• "PS Analysis: The 2011 WingNuts Capsize Practical Sailor". Practical Sailor. April 2012. Retrieved 6 December 2013.
• Rousmaniere, John (1980). Fastnet, Force 10: The Deadliest Storm in the History of Modern Sailing (Paperback). W. W. Norton & Company. p. 304. ISBN 0393308650. ISBN 978-0393308655
• Rousmaniere, John (13 September 2012). "Sailing Accidents: Lessons Learned". Sail Magazine. Retrieved 27 November 2013.
• Rousmaniere, John. "Tests of Sailor Retrieval, Capsize Recovery and Entrapment". US Sailing. Archived from the original on 3 December 2013. Retrieved 19 November 2013.
• Rousmaniere, John (22 October 2011). "Youth sailing 420 tragedy on Severn River report - Organizations". US Sailing. Archived from the original on 10 March 2013. Retrieved 27 November 2013.
• Sharp, Eric (21 July 2011). "Kiwi 35 'probably as stable upside down as she was upright'". Detroit Free Press. SailWorld.com. Archived from the original on 12 December 2013. Retrieved 6 December 2013. including a picture of the turtled Lugnuts
• Smyth, W. H.; Belcher, E. (1867). The sailor's word-book: An alphabetical digest of nautical terms, including some more especially military and scientific ... as well as archaisms of early voyagers, etc. London: Blackie and Son.

• Rousmaniere, John (June 1998). The Illustrated Dictionary of Boating Terms: 2000 Essential Terms for Sailors and Powerboaters (Paperback). W. W. Norton & Company. p. 174. ISBN 0393339181. ISBN 978-0393339185

Look up turn turtle in Wiktionary, the free dictionary.

• Hallett, Peter (1 August 2013). "E-SCOW capsizing and being righted after duel with Kiwi 35 Racing sailboat" (video). Bellingham Bay: YouTube. Archived from the original on 21 December 2021. Retrieved 7 December 2013.
• "Hobie Bob Installation" (video). YouTube. Archived from the original on 21 December 2021. Retrieved 21 November 2013.
• "How to Right a Capsized and Turtled Flying Scot Sailboat" (video). YouTube. Retrieved 19 November 2013.^{[dead YouTube link]}
• Lebigot, Sebastien. "Righting a capsized catamaran (Hobie Cat speed)" (video). YouTube. Archived from the original on 21 December 2021. Retrieved 19 November 2013.