In the US, you need no license to use a VHF (either fixed or handheld) from a vessel while on the water. Most radios (both fixed and handheld) come with the weather band channels, I think (certainly every one I've seen has...)
Note that, in the case of a real emergency, nobody really cares who's licensed for what: yell for help and get everyone safe, then worry about consequences.
If you are new to boating, Chapman Piloting is a great reference for most things you should know. Available through Amazon, West Marine, and probably most larger boating stores.