They get their common name from their habit of swimming rapidly in circles when alarmed, and are also notable for their divided eyes which are believed to enable them to see both above and below water.

In fact their shape is a good first approximation to an ellipsoid, with legs and other appendages fitting closely into a streamlined surface.

Their integument is finely sculpted with little pits; it is hard and elastic and produces a water repellent waxy outer layer, which is constantly supplemented.

[1] In this respect they recall the horizontally divided eyes of the four-eyed fishes (Anableps), which also live at the surface of the water.

In general the adults occupy areas where water flows steadily and not too fast, such as minor rapids and narrows in leisurely streams.

Such studies are of interest in research into aspects of nanotechnology because the beetles' motion may be expected to provide insights into how groups of robots might coordinate movements.

The economies that the beetles can gain by suitably adjusting their positions within the group, are important when individuals swim against the flow of a stream.

[citation needed] The beetles could use the waves generated by their moving as a sort of radar to detect the position of object on the water surface around them.

However based on molecular evidence they are currently thought to be the earliest diverging lineage of the Adephaga, and to have evolved their aquatic ecology independently from other adephagans.

Cladogram after Vasilikopoulos et al. 2021[5] Gyrinidae Trachypachidae Cicindelidae Carabidae Haliplidae Noteridae Hygrobiidae Aspidytidae Amphizoidae Dytiscidae Taxonomy after[6][7][8][9]