Backswimmers are other predators that can also inflict a strong bite.
They are backswimmers because they do indeed swim upside-down through the water. Their hind legs are very long and modified for use as oars. Because they swim upside-down, their body is shaped similar to a boat with the upper surface of the body keel shaped. Another adaptation for their back swimming behavior is that they are counter-shaded opposite of most creatures. Normal creatures have the upper body surface darker than the lower surface since this makes them less conspicuous.