After you complete the Mazercise puzzle, you will find yourself face-to-face with Montgomery Gator. Leaping onto the catwalk, he will smash one of the turrets you need to complete this encounter before chasing you around the area. During this sequence, you must fill the Splash Bucket located at the far end of the room, prominently illuminated by big bright arrows. Here’s how to fill the Splash Bucket in Five Nights at Freddy’s: Security Breach.
First, you must locate turrets around the arena, like the one pictured above. These will fire little plastic balls, but each turret only gets 10 shots before needing to recharge. You should aim these turrets at the Splash Bucket and fill the meter overhead. Be warned, while you are attempting to do this, Monty will hunt you down — and not only does he still have his leap attack, but he also will jump from location to location, often right in front of you. He will also periodically destroy turrets, so your options will become more and more limited as the fight progresses.
Once the meter is full, dash to the button underneath the Splash Bucket, which is illuminated by a spotlight. This will trigger a cutscene and end the encounter. Congratulations, you now have Monty’s Claws, an upgrade for Freddy that will allow him to slash through chained up gates with a Monty Symbol on them.