One thing about the jetski rentals in the past: The skis are stuck in 'learners mode'. That means you're limited to about 15mph. While you can get up on plane, you aren't going to be jumping any waves. Plus, they wanted you to stay in a particular area. Even my non-thrill seeking wife called the learner's mode and limitations on where you can go "fun killers".
I rented a pontoon boat from them. 24 feet long, and powered by a puny 9.9 hp mercury 4 stroke. While it did move the pontoon boat around Bay Lake and the 7 Seas Lagoon, it didn't do so very quickly. And, docking with such a wimpy engine was an adventure due to waves from other watercraft.
One thing more thing that kind of frightened me (who has 30 years of boating experience with high performance boats) about driving watercraft at WDW is that the ferry boats do NOT yield right of way, nor follow regular boating rules. They assume everyone will avoid them, and yield to them. Not a big deal, until you want to take the water bridge between Bay Lake and 7 Seas Lagoon. Then, you'll encounter the big ferry boat in the channel in front of the water bridge, and the smaller, but still large, "friendships" that go between the MK and the resorts on Bay Lake running down the middle of the channel on the water bridge and the approach to the water bridge, leaving no space for you in a pontoon boat.