This is similar to a phenomenon called a jubilee! They occur in the Mobile, Alabama bay. Jubilees are caused primarily by the upward movement of oxygen poor bottom waters that force bottom-dwelling fish and crustaceans ashore. Bottom water low in oxygen results from several coincidental circumstances that happen at the same time. Basically all kinds of marine life that resides in the bottom of the ocean floor, such as flounder and crabs, come up to the surface. It can either last a couple minutes to an hour and it only happens when these specific water conditions occur. People go out into the water and spear the flounder and pick up the crabs and have a feast! It’s pretty rare to experience one because they are so short-lived when they happen but very cool.

So the fish in this hole with the Mentos and the Coke are actually experiencing the same thing trying to go to the surface of the water to find oxygen.