USA (California) Boaters...

Depends whether a commercial or private boat. No certs for a private boat needed, just common sense.

Awesome... this will get interesting of course.

Valid drivers license here in nyc.

Just need to register your boat. It is good to go here:
http://www.dbw.ca.gov/pubs/ABC/

And read each of the chapters... While you don't have to pass any tests, you do need to know the regulations and cops on boats love to give out tickets to newbies.

Especially read the required equipment, especially if you plan to bring minors on the boat.

Not sure about Cali but I like what Washington State started doing a few years back. Boaters are required to pass an exam pretty much like a driver's test that includes rules and regulations for safe boating.

Over the next few years a new age group is required to take the exam and get a card. Currently it's age 25 and younger, in 2010 it's 30 and younger, etc until everyone is required by 2014.

As far as a boat goes, if you are bringing one into the state you have 60 days to register it. If buying one in state, you have 15 days. Some boats require Coast Guard documentation along with State registration.

As long as you do not get a boating ticket the requirements are the following in CA:

California law requires a person to be 16 years of age or older to legally operate a vessel powered by a motor of 15 horsepower or more, including personal watercraft (PWCs).

Exceptions to this law are:

Persons 12 to 15 years of age may operate a vessel powered by a motor of 15 horsepower or more, including personal watercraft, if they are supervised on board by a person at least 18 years of age.
There is no age restriction for operating a sailboat under 30 ft. long (with wind as the main source of propulsion) or a dinghy used between a moored vessel and shore or between two moored vessels.
It is illegal to permit a person under the age of 16 to operate a vessel powered by a motor of 15 horsepower or more, including personal watercraft, without onboard supervision by a person 18 years of age or older.

basic US rule: if your life is on the line, then you probably look into safe operations before proceeding. i kinda dig that...