One lost his footing and is now
just floating around on the surface.

Sounds to me like it could be dead. Pick it out of the water and have a look
inside.

IME, this is perfectly normal behavior for apple snails. They have lungs as
well as gills, and when their lungs are filled with air, they float. They seem
to like doing this. Generally, as long as their shells are closed, they're
alive.


Leigh

http://www.fortunecity.com/lavender/halloween/881/