These bugs, are the giants of the bug world - adults may be up to seven centimetres long. The Giant Water Bug positions itself head-down on a submerged plant stem and hunts by ambush, taking tadpoles, small fish, frogs, snails and aquatic insects. It catches prey with its grasping forelegs before piercing the body with its sucking mouthparts.
They are found in eastern Australia, in still lakes and ponds.
This one was found at Bunnings in Caloundra! Not sure how it got there, they do fly so maybe it flew in from the surrounding creeks.