Cayman boat trip. Extra Items?

[Jaydiver]

I have read many of your posts, taken in the pros and cons ---> I am going to the Caymans on the Nekton Rorqual May 13-20, going solo. There are 28 people on the boat so far (max.34).

This is my first live-a-board trip.

My question is what extra items should I bring, that this boat or boats in general do not have on board that you wish you had brought along?

Thanks in advance.