c/f brought this question up to me so this is why he is asking. Note that the will not fly it but only use it on the ground and on water. If it doesn't go airborne then there is no reason why he should have to use aircraft frequencies. If he does decide later to make it so that he can fly it, then he should go with aircraft frequencies. I'd like to have one myself but I wouldn't fly it either, then it would be classified as an airboat.