Dan Diamond in Fishy Business

As Dan Diamond, PI, you awake on a sandbar in the middle of an ocean with no company but the space ship you skilfully landed at the end of Lost in Space. The ship refuses to talk, except to mumble about learner drivers and to tell you to go away. So denied entry to the ship and any conversation there seems little else to do but go swimming. Perhaps civilization is closer than it looks and maybe, just maybe, you will find the one who sent you the message that got you into this mess.