We always use a nylon net laundry bag, a hunk of salt water soap, and 30-40 ft of line and drag it behind the boat for a couple of hours!! works great and ya still need only a small amount of fresh water to rinse the salt out and line dry! Works for us and is easy !! It may be the OLD way but it's still a good way !!
.... and if you get hungry you can just pick the jellyfish, krill and shrimp out of the seams in your cloths.
One thing about cruising and living aboard, it is great fun for awhile but if you really want to make it a long term proposition especially for your spouse, try not to give up to many of the shore living luxuries. Camping is really only fun for a week, save your marriage, get a washing machine, (Spendide) and the systems that can support it . Learn how they all work so you can fix them yourself.
Looking for the dimensions of the smallest available 220 volt washing machine that I can fit aboard Toodle-oo! Laundry was a major hassle this year on our first 6 month cruise - next year will be even more challenging probably since we'll be in the cooler Baltic/Scandanavian areas...