can your portable wifi be use on cruiseship?

We are sailing on royal Caribbean Cruise Ship around japan, if we rent portable wifi, can this provide internet service while sailing?

Hello.
I guess that you can't use portable wifi on the sea,because wifi radio waves don't nearly reach to ships on the sea.
I traveled around Japan coast on a cruise ship last year,but I was not able to get wifi radio waves on the ship.

That's really a question for the company you are renting the portable wi-fi from whether the cell signal is strong enough to reach a ship off the coast.

Exactly. Since the portable wifi device converts cellular signals into wifi, it is the range of the cellular towers that determines if you can get a signal. Usually ships at sea will not get any cellular signal from terrestrial towers unless they're at port.