A:AnswerFRS radios are legal to use in U.S and Canadian territorial waters and in international waters while on ships registered in the U.S. and Canada. The radio user must obey the laws of the territorial waters of the country they are in. If in international waters, then it will be by the laws of the country of which the ship is registered.
The radio range will vary on a cruise ship depending on the size and number of obstructions between the radios. Radios with more power will have an advantage.