My wife and I try to get off the boat daily for a power walk and other exercise, along with calisthenics/stretching and resistance exercise while aboard. In previous years I've brought along flat-sided dumbbells, which are excess weight 99% of the time, and difficult to secure.

This year I bought a set of "Bodylastics" resistance bands for our vacation cruises and was so pleased with them, that I'll probably continue using them for most of the exercises at home I used to use weights for. They have a clip system, with the resistance (in pounds) for each color band stamped into each metal clip, so you can easily and quickly change resistance levels by adding or removing parallel bands. Each color is a different level, so for instance you can add 8 and 19 and 5 to get 32 pounds of resistance.

This is what I bought: http://www.amazon.com/gp/product/B006NZZH18/ref=cm_cr_thx_view

I'm very impressed with every piece in this kit. It all is very well made and designed. It's a tremendous bargain. They also have a web site that shows workout videos using their product: http://www.liveexercise.com

I have used other resistance bands but they were junk compared with these. I have no personal or profit interest in the company. I'm just a satisfied customer spreading the word about a good product. I also use them underway, along with stretches, when I feel like I've been sitting too long and need to move.