Turtling (sailing)
A boat is said to be turtling or to turn turtle when it is fully inverted. The name stems from the appearance of the upside-down boat, similar to the carapace (top shell) of a sea turtle. The term can be applied to any vessel; turning turtle is less frequent but more dangerous on ships than on smaller boats. 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).