Here's a revolutionary idea!
If you plan to live in a marina and never move your boat, consider converting your liveaboard bathroom into a closet and use the marina restrooms 100% of the time.
Marine toilets are among the most aggravating things ever invented by mankind. If you can get along without one, you will be blessed. If you can't do that, here are some ideas.
The picture below is of AWOL, my Island Packet 26MKII.
It is a pretty conventional setup with the manual head, small sink and telephone shower. It has more stowage than many larger boats.
The standard marine toilet is operated by a pump handle. When you've finished using the toilet, you pump the waste out of the bowl into a holding tank. The flushing water comes from raw water (overboard), and requires a through hull fitting to supply the toilet. A Y valve can be turned to discharge the waste overboard instead of into the holding tank. Many liveaboard boats in marinas are required to have marina staff install a lock on the Y valve so it can't be discharged overboard.
A macerator toilet is similar to the standard marine toilet but has a grinder pump with sharp blades that pulverizes all of the waste before it is discharged. The grinder pump also sends the waste to the holding tank or overboard. In some cases, the macerator toilet can be connected to an incinerator that turns the waste into ashes. These installations require a fair amount of space and installation expertise and use a lot of energy.
Another kind of toilet that some people have used successfully is the composting toilet.
In this device, the solid and liquid waste are separated and the solid waste is "composted" in a peat medium that can be purchased at any garden store. Once you have used it, you crank a handle that mixes up the stuff and sends it to a composting compartment.
The toilet does not need a through hull for raw water, but it does need a vent for gases created by decomposition. The vent is usually installed with a small fan that can be solar powered or draw very little battery energy. The waste is removed periodically and can be disposed of at any marina or used in your home garden.
The composting toilet is about as "green" as any marine waste disposal system can be.
Some people also swear by the "porta potti"kind of toilet. It's free standing, has no plumbing and all solid and liquid waste is deposited in the base of the toilet. When full, it can be lugged to the marina bathroom and flushed away - if the marina allows it.
Other than the old oak bucket, this is the simplest kind of liveaboard toilet. If you have kids, emptying this toilet is a good chore for them and will teach them first hand one of life's "dirty jobs".
Only the larger boats have enough room to have a stand up separate shower compartment.
Here is a photo of a Nonsuch 30 Ultra sailboat with a separate head and shower. It's an unusual feature for sailboats, but the Nonsuch is very beamy with a catboat rig that puts the mast way forward and allows for a spacious interior.
Power boats are more likely to have this luxury than are sailboats because of the space consideration.
Usually the shower is designed with a portable shower head so that you can either sit on the toilet or above it and direct the shower stream over your body.
Even though some of these arrangements include a shower curtain, you will find the bathroom compartment still gets very wet and has to be dried off as much as your body.
Here's a look at the head on my CSY 33 Silverheels.
Beware of boats where the shower drains directly into the bilge. All it takes are a few showers and your bilge will start to smell to high heaven. Long hairs and beard stubble and soap scum will plug up your bilge pump. That could sink your boat.
It's best to drain the shower into a separate sump and then pump the sump contents into your waste holding tank.
Most liveaboard bathrooms have a sink with both hot and cold water. The sink counter top is usually okay for one man with modest toiletry needs like a razor, shaving cream, deodorant, comb, toothbrush and tooth paste. Most women need a lot more space than the average liveaboard boat provides. Men may decide not to shave and to stop using deodorant and tooth paste.
It's nice to have some dry place to store stuff like toilet paper or clean towels. Unfortunately, most liveaboard bathrooms are also showers and dry storage is hard to accomplish. A big plastic container with a snap seal lid can be handy in these cases.
The toilet itself will have a manual pump or an electric macerator pump, but you can also get electric models to replace the manual version. Just remember the energy cost. The sink and shower will also be served by a single electrical pump, and the sump will also have a small pump to get rid of shower water.