The FrogLog Animal-saving Escape Ramp for Pools 

This works 100%. Four years using two frog logs in a very large pool, and not a single floater, whereas before the frog logs, there used to be regular casualties (chipmunks, mice, small rabbits etc). You can use dive weights inside the weight pocket instead of sand for extra stability, or even just put a rock or small brick over the flat pocket. They're super durable too. I just do a thorough clean every fall, but there's never been a hole and it doesn't even seem to lose air. In four years, I've only had to add air twice. Highly recommended.