can they swim?
Yes, several families of Heteroptera are "water bugs", adapted to an aquatic lifestyle
Hemiptera
Several families of Heteroptera are "water bugs", adapted to an aquatic lifestyle, 
what is a unique characteristics of insects in the order hemiptera check all that apply The group is very diverse. The majority of species are terrestrial, including a number of important agricultural pests, but some are found in freshwater habitats. how do they produce sound? Many hemipterans can produce sound for communication. The "song" of male cicadas, the loudest of any insect, is produced by tymbal organs on the underside of the abdomen, and is used to attract mates.
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Hemiptera [SEP] Swimming and skating
Several families of Heteroptera are "water bugs", adapted to an aquatic lifestyle, such as the water boatmen (Corixidae), water scorpions (Nepidae), and backswimmers (Notonectidae). They are mostly predatory, and have legs adapted as paddles to help the animal move through the water. The pondskaters or water striders (Gerridae) are also associated with water, but use the surface tension of standing water to keep them above the surface; they include the sea skaters in the genus "Halobates", the only truly marine group of insects.