Complex sentence: Distraught, he decides that to slow down the ship, he will jump off into the water, dressed as if for tennis so he can easily swim-this way, they will have to stop and turn around to rescue him.
Split into simpler sentences: Distraught, he decides that to slow down the ship, he will jump off into the water, dressed as if for tennis so he can easily swim. This way, the ship will have to stop and turn around to rescue him.