Is it safe in case of rough sea? and the boat moves?

Think so. the plexiglass is very thick and not in direct contact with anything really, also it is covered by plywood when the floor is 'closed'.

Showers every day ? Gollygosh ! Maybe you should turn down the expectationmeter a little.

Your boat isn't big enough to carry enough diesel to make enough electricity to make enough water to give you a shower every day.

Try a shower every 4th day and see how that works.

Don't worry, we have made good calculations on this matter. We have the diesel tank, extra fuel tanks, air generator and solar panels to receive additional electricity plus also another fuel generator.

The Katadyn PowerSurvivor/watermaker consumes only 16 amps per 20 liters produced water (5,2 gallons). 20 liters per day is well enough for quick showers, making the dishes and hopefully there'll also be some left for cooking/drinking. Although we'll be carrying additional drinking water in bottles.