Sea Trap

A Sea Trap is composed of two sea urchins holding some wire-like material between each other, in the form of a sort of tripwire. These nuisances will randomly pop up to block Link's path while he travels through the Great Sea on Linebeck's Ship. Although it is possible to attack the two urchins that bind the wires with the cannon, it is much easier to just jump over them. Since they're immobile, it's also an option to stop and change course to avoid them completely.

Trivia

 * Sea Traps are the only enemies Linebeck directly explains how to defeat. Because of the explanation scene, a Sea Trap will always be the first sea-borne enemy Link encounters in Phantom Hourglass.
 * Before Link grabs the Cannon on Cannon Island or leaves the Southwestern Sea, Sea Traps are the only living enemies that will appear on the sea.
 * Sea Traps are the only enemies which can be completely avoided by boat-jumping in Phantom Hourglass.