Dolomedes triton hunts at an interface. It sits at the edge of still water with the front pairs of legs on the surface, and the vibrations arriving through the film tell it where a struggling insect is and roughly how large.
Movement across water uses two gaits. In rowing, the legs sweep like oars and press dimples into the surface without breaking it, driven by surface tension and drag. In a faster gallop the spider effectively runs, lifting clear between strokes. Its water-repellent hairs keep it on top.
Diving is the escape route and sometimes the hunt. The spider pulls itself down a plant stem and holds on, wrapped in a silvery film of air trapped among body hairs that also serves as a small oxygen store. Most of its prey is insects, but tadpoles and small fish are taken, which is where the family's name comes from.