That is true however a carrier that hovered over water that could also pass over land would be vastly superior, especially if you were on a world where oceans might not even exist or exist in a form that could not provide proper bouyancy, like it there was a high concentration of methane in the water etc.
Id never green light a project to another planet that said we were gonna drop a boat hehe.
http://img.gamespot.com/gamespot/images/2006/124/reviews/932358_20060505_screen002.jpg Thats from battlefield 2142 it was a carrier/base floated over the city acted as a base launched air craft etc.
Thought it was great