Unfortunately, the government is not well suited to judging who is and isn't capable of boating safely, and as such will tend to set the bar fairly low. Unless all of the fees from the boater licensing process are going to improving waterway infrastructure and safety... I'm really not in favor of wasting more money on the government.
As for the comparison of a plane to a boat... planes always fall out of the sky if the fuel runs out or you do something majorly wrong. Boats do not always sink, nor do they always hit someone else... comparing a boat, especially a sailboat, which generally has a relatively low top speed, to a plane is sheer fallacy. With the exception of multihulls and some of the larger boats, like GUI's, most of the sailboats found out there are going to be lucky to get up past seven or eight knots... Not exactly fast enough to be a menace in most cases.
Licensing and mandatory education for powerboats, which have the ability to get up to ridiculous speeds, where control and skill is a factor, especially on things like PWC, would make far more sense.
When was the last time you heard of a fatality involving a speedboat and a sailboat, where the sailboat killed someone on the powerboat and the sailboat was at fault???—Never, at least as far as I've heard.
When was the last time you heard about a powerboat killing someone on a sailboat, where the powerboat was at fault—Clear Lake, Ca; Buzzards Bay, MA; etc.. that's far too common.
Sailboats can kill people too. I remember reading not too long ago about a sailbnoat strking another sailboat at night while at anchor and killing almost everyone who was down below asleep (because they were anchored at night). Also, should I bring up our friend Ronnie or others that have followed in his footsteps??
Putting together a license like we use for cars would not be the most helpful thing in the world... but it would help. It would stop the impulse boaters. I dissagree with anyone who thinks it would not help some. At least they might learn rightr or way and basic navigation.
However, I think for boating, it should be as stringent as flying or like a 6 pack/captain's license. I think it should be involved based upon the tonnage you carry. I think for a ski boat... a "drivers license" type of license. For a large Sea Ray, a tonnage type of license.