Bite
Bite in the direction you are looking. Turn the camera at least 90 degrees to either side to use a side bite without turning the Sarco first.
Controls:LMB
Death Roll
Roll while attacking a target.
Controls:RMB
Lunge
Hold the key to raise a crosshair and lock onto a creature ahead, then release to hurl the Sarco at it with a bite. Nothing happens unless a target is locked, it costs a large chunk of stamina, and it cannot be used while swimming.
Controls:Hold C, then release
Default PC controls. Custom keybindings may differ.