Jet skiing is similar to Snowmobiling (Which I will write about in a later post) You go about the same speed, on a similar machine. Only you do it on liquid water instead of solid.
Water is softer and warmer than snow, so you don't need gloves and some don't bother with a helmet. But I advise you to use a helmet anyway - you can still exceed 50 mph, even if water is softer than the ground. You can be thrown off and hit your head on your own jet ski, not to mention you can collide with other vehicles. Of course, if you are a slow poke that hates speed, and can't get the nerve to go as fast as I do, then perhaps you don't need one ;-D
Jet Skiing can also be used to pull people. You can pull smaller kids on a float, or people water skiing (see my post in July). This is a lot of fun for both the kid and the adult (be careful about turning too steeply.
Jet Skiing is not cheap, even renting. It isn't hard to do and doesn't take a lot of muscle, but it does involve some. If you fall in love with them (and have access to a lake/ocean), you can buy one for less than the cost of a motorcycle.
Jet Skiing trends male. We like to go fast. Laws vary by state, but usually you can do it you are 16 or older. Some areas require you to take a boating course but let you do it as young as 12. In general, most states let a younger child ride on the back of a jet ski, even if they can't drive it. Some larger jet skis are designed to hold 3 people. (They also sell something called a shuttle craft, which is an add-on floating boat for your jet ski. You drive the jet ski into, lock it down, and boom, no you have a 6 person boat.) Kids tend to like jet skis a lot, even if they can't legally pilot them.
If the water is cold, you may want a wet suit. Foot ware (water shoes) is a good idea. Don't forget sunscreen and sun glasses if you do not use a helmet.
Wear a life jacket - even if you can swim, you can be knocked unconscious.
My stepfather owns one, but you can rent them near NYC, or pretty much any lake/ocean side resort. Here is one of several sites to book tours at in NYC (chosen because they posted their prices on the web - I like to reward good behavior):