Cutthroats

Taken from mobygames.com:

You live on a small seaport island called Hardscrabble – hardly the hip place to be. Working as a professional scuba diver, you have the chance to salvage a sunken treasure from one of four shipwrecks, earn the respect of all the old farts and become wealthy beyond all imagination.

http://www.mobygames.com/game/dos/cutthroats