These engaging little beetles can be seen whirling around and around on the surfaces of dykes and pools throughout the Reserve. They are the colour of burnished metal, and seem almost to float like little hovercraft, so fast do they move! They have special hairs on their legs to make them into paddle shapes, which they then use for swimming with both on and under the water. They are also noted for their unusual eyes, which are divided into two for seeing above and below the water at the same time.

They are thought to collect together and perform this strange dance as a protection against predation. Indeed if you try to follow their movements it can be quite difficult, just as it would be for a passing bird or frog. Their food is largely small insects which fall onto the surface of the water. By moving quickly they probably also increase their chances of finding the food before their neighbour does.

The beetles can swim, and breathe underwater by means of a bubble of air which they take down with them. This makes them very buoyant, and means that to remain underwater for very long they must anchor themselves onto a plant stem or the like. However they must eventually rise to change their air bubble, not because they run out of oxygen, which diffuses in from the water anyway, but actually to dispel the carbon dioxide which builds up in the bubble and will not diffuse away as fast. They will often dive down in unison to avoid a predator or rough water. They can also fly, having perfectly good wings hidden under their burnished wing-cases.