Some sort of amplifier will be needed for sure. I'm not sure if the TV out jacks will work - it depends on the TV model and the hookups.
My suggestion would be something like self-amplified PC speakers. Cheap, yet with decent sound. Biggest issue I see is the distance from the receiver to the pool - you might have to use killer cables, or even a pre-amp. Just depends.
Of course, if you ran the satellite receiver through the stereo system everything wins - you now have a home theater, and use the "B" speaker outputs to drive the pool. Of course, I'm making some assumptions here, but you get the idea of the possibilities.