We went the pool net route when our daughter was little. Sure beat dividing up our small backyard with a fence. Our pool is an odd shape, the deck has different elevations, and there's a rock waterfall. The net works fine with all that.
Fences can be scaled and gates can be left unlatched. If the net is on the pool there's no way a kid is getting in there.
http://www.katchakid.com/