The great diving beetle (Dytiscus marginalis) is an aquatic diving beetle native to Europe and northern Asia, and in the UK is common in Wales, much of England and southern Scotland but less common on chalk and in the far north.

They are dark-coloured (brown to black) on their back and wing cases (elytra) and yellow on their abdomen and legs.

A voracious predator, this beetle hunts a wide variety of prey including small fish.

The first two pairs of legs of the male are equipped with numerous suction cups, enabling them to obtain a secure grip while mating, and on their prey.

The beetle reproduces by laying eggs under water in the mesophyll of an aquatic plant leaf.