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Since the gravitationnal acceleration is 9,81 meters per second^2 you could try to find the decceleration in water and calculate the highest point you can jump from. I could do it for you but I don't know the decceleration in the water but it just needs a little bit talent in physics.
Or to have a less accurate answer, but a good one, I think you can compare with divers. At our town's pool, there's a 5m diving board and the water is 4,5 m deep but people don't go past 3 m. So for 5m high you go 3m deep. So for 7feet deep you can go 11,67 feet high (I think it's this but I maybe wrong). And since you have your skis, they'll probably slow you down a lot so I think you could go 15 feet high maximum.
I hope this help you because I tried my best but if you want, I could ask my physics teacher and i'm sure he'll give the right answer but I believe i'm right.