why would my red apple snails come out in hot water and than sink back in to their shell i the tank?

Answer 1

The other poster is correct. If you want more infomation on them then check out http://applesnail.net/

Answer 2

I would assume that the water in your tank is not warm enough for them.

The optimal water temperature for apple snails lays between 18 to 28°C (65-82°F). As with many cold-blooded animals, apple snails are more active at higher temperatures. At higher temperatures, they eat faster, creep faster and they grow faster. Also higher temperatures mainly induce the reproduction of the apple snail. At lower temperatures (18°C/65°F) the apple snail enters a dormancy state in which they creep away in the mud and become very inactive. Temperatures below 18°C/65°F should be avoided as the mortality rate quickly increases.