While most of the advice you have gotten is sound, the most important thing is not to take it personally. The chemistry was not there for him.....period. Thats enough of a reason for him to want you off, and thats no slight on you.
I dont think its necessary to find out why, just be comfortable in yourself. You dont need to learn how to interview 10 times better, because thats something you cannot do in reality, however you can in your own mind. We all work harder than the guys beside us....we all think that way too.
I agree with Rockdawgs advice about checking in with your boss,,,captain,,person who makes the decisions to see if you are on the right track and ask for things to improve yourself and your fit into whatever "team" you are joining.
The most important thing though...and this is what I mentor my 45 managers with is to feel comfortable about who you are, not try and fit some preperscribed mold. Many of us search for that opne person to feel comfortable with in our lives....the same is to be said about the job you take,, and even the adventure you had planned. This captain didnt feel the chemistry...so better to find out nowthan the Azores or in the middle of the Atlantic, Nothing wrong with you mate......just wasnt meant to be. Find another ship...another captain.