There are two main types of sewage management on narrowboats; one has the toilet discharging into a big holding tank, which, when full, has to be pumped out at a shoreside pump-out station, and the boat needs to be moved to that station. This is a bore, and costs about £25 a time.
The other system uses a small portable tank that slots in under the toilet; when you want to empty this 'cassette', you simply slide it out; the flap that closes off the top orifice should have a watertight seal, so it's quite mess-free (I had to replace the seals on my tanks, which was a fairly straightforward job and well worth doing, eccchhh). Then you can take the cassette to a sani station, which may be several miles from where you're moored, but at least avoids an unnecessary voyage.
I empty my tank weekly at the moment. Some people don't put loo roll down the hole, but bag it up and either burn it or bung it in a rubbish bin. I'm not really comfortable doing that.
I'm moored at Semington at the moment, and the nearest sani station is at Seend, which is about two miles away. On a summer's morning, it's a fine trip on the bicycle, even with the shit tank rattling on the trailer.
I take a plastic raincoat, a pair of rubber gloves, and a dedicated brush for cleaning up the mess. Here's the sani station at Seend.
So now I can enjoy the towpath, where the meadowsweet and the spiked speedwell are now proliferating
and the heron pretends it isn't there