How does the swimming motion of a Hydrophilid differ from a Gyrinidae (whirligig beetle)?

Hydrophilids move with a jerky, somewhat clumsy motion and may hover submerged, unlike Gyrinidae which skate frantically on the surface film

Observational differences in locomotion provide a quick way to differentiate common aquatic beetles in the field. Water scavenger beetles (Hydrophilidae), relying on their sub-elytral air bubble, often exhibit a swimming pattern described as jerky or clumsy as they navigate the water column. If they surface, they might maintain a slightly elevated position just under the film while recharging their air supply. Conversely, whirligig beetles (Gyrinidae) operate entirely on the surface tension of the water, moving with rapid, frantic skating motions, famously leaving behind two distinct, symmetrical V-shaped wakes trailing backward from their bodies.