Most boats operate on either 12 volt or 24 volt, other voltages are rare but also used. These low voltage systems are usually more than adequate to run the majority of appliances you should need on board your boat. 12 and 24 volt boating equipment is specifically made to work from power provided by batteries, similar to your car battery.
Low voltage boat lights, solar panels, horns & wiper motors and more components are available. It is also possible to setup mains power, also known as shore power, to supply 230 volt power. This can allow you to run your low voltage equipment when plugged in at your mooring and is worth considering to conserve battery power.
There is 1 product by Adlard Coles Nautical in the Boat Electrics category.