There’s a recurring topic on one of the main sailing forums: How To Combat The Smell In Your Boat’s Bog. I mean head (if we’re using the correct nautical terminology, because that’s what mariners call their bog). Seagoing boats have a marine toilet. This is commonly what they look like:

You pump in seawater, do your business, then pump out the, ahem, business, then pump in some more seawater to sluice it all away and Robert’s your mother’s brother. Except seawater, being salty and all that, has a natural smell of its own. And the human by-product, no matter what state of liquid or solid, also has a smell of its own. And when you combine the two types of smell there can be an interesting and not altogether welcome olfactory experience.
The learned folk on the aforementioned sailing forums say one should flush out the head with freshwater. And this is a remedy I’ve tried and can endorse. We do this kind of thing because the use of any kind of chemicals for cleaning and/or pong eradication is Very Strongly Frowned Upon, because it’s not green you see. Not withstanding the lack of greenness of the human by-product that you’ve just pumped into the sea. But this is how it is, I’m not here to make sense of the rules or even to make the rules, just here to follow them.
Because freshwater is a scarce thing on an seagoing/oceangoing vessel, there are those who bypass the whole seabog experience; just do their thing in a bucket and empty it over the side. This process is known as ‘bucket and chuck it’ and yes, you can see why. Brings a whole new dimension to the phrase ‘feeding the fish’ though. But I’ve stepped in worse things on the floor of the toilets in many First Great Western trains, and if you bucket and chuck it with skill (and attention to wind direction), you won’t get your by-product flapped back into your face.
I suppose just hanging your arse over the back of the boat is also frowned upon?
Maybe only if you are moored up.
The thing with hanging your arse over the back/side/front of the boat is that you tend to fall overboard and that puts you in the shit in a whole different way