What are great opportunities to capture while on a cruise?

I'll be going on a cruise to the Roatan Islands soon and I was wondering what are some of the opportunities, on the boat, are worth capturing? I'm only taking 2 lenses (17-50mm and 55-250mm) with my Canon T2i. No filters, no tripods either. I'm just looking for tips and hints to be aware of when I'm on the boat. I'm not sure what excursions I will be participating in right now.

--
I'm here to learn