T-pushups, dips, and pull-ups (palms away) and chin-ups (palm toward you)
Your boat might have hardware you can perform the hanging exercises on...
Also, I have been doing interval sprints and tabata intervals for the past 2 months, and have lost a considerable amount of fat while maintaining all the muscle I've gained through strength exercises. These may sound easy - I assure you they're not.
Interval sprints: sprint as hard/fast as possible slightly uphill for 15 seconds, jog back to where I started. Repeat 8 times.
Tabata rope: jump rope as hard/fast as possible for 20 seconds, rest 10 seconds. Repeat 8 times.
I've done these 2-3 times a week with terrific results. I hate doing cardio for more than 10 minutes. And as you can see I try to keep it under 5 mins.