One of the fish probably strapped an explosive vest onto itself and went out in a blaze of Piscine glory.
I remember a cellar bar in Marysville CA fifty five years ago in which you could watch swimmers in the motel pool next door .
One night someone drove by the motel and threw a stick of dynamite into the pool. AS water does not compress, the blast knocked out the window into the bar flooding the patrons.
Lucky no one was in the pool, and the bomber was later caught.
Wonder if someone dropped an explosive into this pool.