Here are my thoughts...
First, the jet ski is out of the box thinking. I like people thinking outside the norm. I can't see a jet ski as being very effective, since water chemistry and biology is dynamic. With water pushed downward, displacement with a that amount of vertical movement can help for that moment. Something consistent, such as bottom-diffused aeration, or circulation which moves water toward the atmosphere, allows gas exchange at the surface on a regular basis.

But, I think the better answer is to not worry too much about oxygen levels. When your pond drops and maintains a level, your fish adjust their numbers to fit the habitat and space, meaning that lots of fish are eaten. If your pond stays at that level for months at a time, then the population of fish stabilizes and doesn't really create an overabundance for that environment.

But, if you are feeding fish and not harvesting many, then I can see water quality degradation as a potential problem.

Teach a man to grow fish...
He can teach to catch fish...