Aquaman has lost a hand on numerous occasions. For some reason, it's a fate that keeps on befalling him, but on the plus side he usually replaces it with a badass harpoon or some other cool weapon.
This was originally the handiwork of of a villain named Charybdis, who deprived the Atlantean king of his ability to communicate with marine life and shoved his left hand into a piranha-infested pool.
Once the carnivorous fish were done eating, there was nothing left of the appendage bar bones and a few dollops of chewed flesh. It was a shockingly graphic turn of events and would be too dark for the DC movie universe, even with a horror master like James Wan in the director's chair.
That said, other incarnations of Aquaman have lost a hand, including one which had it severed during an epic battle with Black Manta. Given that Arthur Curry can't seem to keep all of his limbs intact, there's a chance the film will reflect that, but the piranha story is a little too grisly for a mainstream comic book blockbuster.