When there is a rapid change in barometric pressure, aquatic snails can find themselves floating, which is bad news. They become vulnerable to predatory fish. I would presume they are looking for shoreline or emergent vegetation to escape back down the water column.
I’ve caught trout that have obviously been gorging on snails. It’s one of those mystery hatches where you see rising trout but can’t figure out what they are eating. Eventually, you find a snail upside down under the surface film and it clicks.
