When you're out of the US Coastal waters (as close as BC, Canada) is it legal to pump your marine toilet directly into the sea. There just aren't pumpouts available in every remote cranny of the earth like there are in Puget Sound. This is kind of like you wouldn't poop in your neighbors yard (unless they live in BC), but for extending backpacking trip its considered acceptable to use a cathole.
Our current toilet situation on Deep Playa is that we have a Wilcox Crittenden Imperial toilet and instead of a rigid fiberglass holding tank we have a 20 gallon bladder into which everything is pumped. We're also setup with a macerator (like a garbage disposal) that can be use to grind up everything when you're in an area where pumping directly overboard is acceptable. This also keeps fish from having to swim around with toilet paper stuck to their tail fin. Well, the toilet doesn't pump very well (I bent the handle this weekend), using bladders as holding tanks is kind of a nuisance (you have to lift them while you're pumping) and all of the plumbing needs to be replaces because it smells (this can happen as they age).
Instead of doing all that work we've decided to go with a MUCH simpler solution, the Nature's Head Composting Toilet. The basic system is that urine is captured is in a bottle and your poop is composted along with some peat moss or coconut husks to absorb water. The urine can be disposed of on-shore in the toilet and the compost can be deposited in any flower bed or bagged and placed in the regular trash. Before you get all gross, read this about compost. And then realize that the fact is on a boat (or in an RV, or camping) you become more intimately involved with your bodily functions, and this was the best option for us given our the attractive ness of eliminating 2 through-hulls and to be as good stewards as possible when we're traveling.
I'll have a bunch of photos and more discussion about this as we move forward with the rip and replace. Right now everything has been ordered and is on-hand ready to go, just need to pump out one last time and start removing the old system.