Not only is peat moss non-renewable and damaging to the ecosystem it is harvested from, when we used it it came with bug eggs that hatched into a bunch of compost-larva. Nearly put the wife off the whole project!
Coconut coir is what we use. Compressed bricks expand many-fold to form a large quantity of a nice dirt-like substance. When they're dry and compressed they're easy to store, light weight and field expedient for boat storage and usage.
Coconut Coir:www.cosmiccoir.com - Coco coir, Coconut coir, Coco peat, Hydroponics, Best coco coir, Growing media, Clean super washed, Coconut peat, Coco pith, Coco coir chips, Coconut husk chips
That's the point I was making earlier. This is not actually composting which is a very environmentally safe and responsible activity.
1. Urine goes over the side. If it's no big deal then invite your neighbors to pee in your pool!
2. Pooh gets dumped somewhere on land, could be laced with fecal bacteria that can cause sickness (unless you store it for a few years - yah right!).
Portable or pump out heads are way above this standard and can easily be disposed of in a responsible and non-environmentally fashion.
You either care or you don't - karma.