Staying in shape on a research cruise?

Hey everyone! I am about to be a recent grad and am going on my first research cruise this summer for about two months…. EEK! I am really excited but am worried that I’m going to gain a bunch of weight just sitting around in a lab for 12 hours at a time. I wouldn’t say I’m a crazy gym rat or anything now but I just want to avoid getting too out of shape. Does anyone have small tips or anything on how to avoid this?? Thanks so much!