The same way you charge a car battery. The only difference in them is that the marine battery is a deep cycle battery, meaning it is designed to be run completely down without damaging the battery. Ideally you need a charger designed to charge deep cycle batteries but you can charge one with a normal battery charger.
plug it in
Chargers don't care is the battery is used on a boat, a car, or whatever. What is important is that you match the voltage of the battery and the charger. Don't use a 12volt charger on a 24volt battery, etc.
Changing a boat battery can be specific to the type of boat. Many boats have a small plastic box with the battery in it, while others have the battery hidden in a compartment.
Unless it is a rechargeable battery you cannot charge a dry charge battery. If it is rechargeable you need to purchase a charger for that size battery. Automobile batteries are not dry charge.
Battery cycling is a process in which a battery's charge is entirely or nearly depleted, recharged, and the process is repeated. In your case, the battery is not designed to do this for safety reasons, presumably battery explosion. As long as the battery is constantly being recharged by the alternator of your boat's engine and not cycled, you have nothing to worry about, aside from standard precautions and preventive maintenance.
No, it takes electricity to charge a battery.
No the battery don't have a magnetic charge.
how do you charge a vespa battery
It depends on the battery charger. Some chargers will detect that they're hooked up backwards and do nothing. More than likely though it will dis-charge the battery pretty quickly, and probably damage it.
A battery charges nothing it accepts a charge from the alternator.
You can not charge a battery in the microwave.
Yes and also you can charge it on a wooden bench, a lawn chair, a flower pot, and a tub along as it isn't full of water.. or if you want to get adventurous you can charge it on a mountain, on a dead goat body, in an airplane, on a boat (along as it isn't sinking), or in your hands aslong as its hooked up to a charger and not in a conductive liquid you can charge an auto battery anywhere. Placement will not affect its charging capabilities unless the battery is dead which is caused by the metal plated in the battery acid being corroded which is unavoidable. It is an old wives tale that concrete kills a battery.