as mentioned above, pool exercises definitely don't help much in terms of plyometric training, because the eccentric component is basically gone.
It can help a bit with pure concentric strength, due to the resistance the water provides. I imagine pool sprinting is probably more effective at strengthening up some muscles involved with sprinting or single leg jumping due to the resisted knee drive.
Anything involving arm swing under water will provide resistance to the shoulders and probably give some small power increases there too, so sprinting, single leg jumping, double leg jumping etc - as long as the arm swing is resisted, this would definitely yield some benefit.
Aside from that, the real power of pool workouts is in recovery (like FDL said), movement efficiency maintenance/improvement, and/or rehab. You could perform significantly more jumps in the pool which could be a great way to get more work in without taxing yourself, especially if you're dealing with some potential injury issues where you want to get some skill work in with much less risk of aggravating the issue (if you were to perform jumps on land).
I'm sore as hell right now, I could definitely benefit from a pool workout to get the blood flowing without wrecking myself with higher impact forces on land.
As for performance, like seifullaah73 said, going "max effort" in a pool is still pretty powerful - you have the max effort voluntary signals to the muscle, without the load of impact/landing. That in itself can still be taxing on the CNS, which is a good thing .. less load on the muscles/joints, but still trying to recruit muscle as fast and explosively as possible. But that's basically a "real training session", though not experiencing as much landing/impact forces, it's still pretty intense. Submax effort would be more of a "movement" session.
Honestly tho, sounds like we need a pool workouts for performance thread in the Peer Review section:
https://scholar.google.com/scholar?q=water+workout+vertical+jump&btnG=&hl=en&as_sdt=0%2C10
