Fiddler crab problem (20 characters)?

Ok we have 2 female fiddler 2 fish (don't know the breed) and 2 golden mystery snails in a 10 gallon (its big enough for them all) anyway theres this pipe that's by the corner and one crab climbs up the pipe and just sits out of the water while the other either is on the floor searching or food or by the other crab. She comes down and eats then goes right back up no that water is not cold (right now its 74') im not worried just curious why shes doing this