Kiddie pools and dogs?

I bought two kiddie pools for my dogs because its hot and I want them to be able to lay in it or play and keep cool. Well my first dog is a German shorthair ponter/lab mix and he actually goes swimming out at the lake and just loves it, but for some reason he wont even consider the kiddie pool in his kennel? Its been in there for 2 days now and only thing he does is drinks out of it like its a big water bowl, but wont step in it. My other dog a pitbull (who likes the lake water but hates baths lol) does the same thing. I've tried luring them with treats, toys and even tossed my ponter in there once and he just hops back out directly after words...??? Any ideas?