Need some training advice...!

Hi there everyone.

This will be my 1st post on here but i have being lurking for a few years now and finally started training full time about 5 months ago.
Being doing great so far, mostly running and biking about 4 to 6 hours a week in total.
I work on a private yacht that travel all over the world (it is not a great as it sounds) and the only reason i have being able to train so much the last couple of months was because we were in a shipyard for a refit and living on land!
But now we are about to sail for 2 weeks and i really want to loose as little as possible of my fitness that i have worked so hard for, i heard somewhere that you loose 3% of your V02 max after 2 weeks and 7% after 3, so i just want to limit the losses by doing some exercise. I have a trainer for my bike but i think the boat will be rolling to much when we are sailing to really get a good ride on that, so what els is left? Core training? I thought maybe skipping?

What would you guys suggest and do in my situation??

Any input or comments are welcome and much appreciated!

Thanks

Philip