Frogmen, also known as Riddler's Frogmen, were men working for the Riddler and Two-Face on Claw Island.
When the Riddler and Two-Face discovered Bruce Wayne was Batman, they invaded Wayne Manor and destroyed the Bat Cave and took Dr. Chase Meridian to the Riddler's NygmaTech fortress on the Claw Island. The Dark Knight and his new partner Robin raced towards Claw Island to save her. Inside the Mother Box, Riddler and Two-Face were playing a game of Battleship with actual bombs in the water and activated them around Robin who was in the Batboat while Batman flew in the Batwing.
On Two-Face's move he hit a button and activated a water mine close to Robin's boat and managed to destroy it but Robin escaped by ejecting before the entire vessel exploded. Riddler and Two-Face cackled as they thought they killed him. Robin put on a breathing apparatus and started to swim towards Claw Island when suddenly nets were fired at him coming from the Frogmen who were dressed in green scuba suits. Batman saw on his radar that Frogmen were approaching Robin fast.
The Riddler activated the bonus round button and from the Mother Box's tips, a burst of green energy blasted the Batwing forcing it to crash in the water. The Batwing transformed into a boat and swam towards Robin who was overpowered by the Frogmen who removed his breathing device and were trying to drown him. Batman ejected from his boat and he and Robin swam away while Batman fired a net around the Frogmen and managed to capture all of them. Batman tied the net and placed it next to an anchor with the Frogmen trapped inside. The Dynamic Duo then swam towards the fortress.