Why don't insects get drown?

Not all insects drown in water. In fact, quite a few live there for at least part of their lives. Insects breathe through holes in the sides of their bodies. If they can't get air in through the holes, they will suffocate. That's why insects that are not specialized for living in water will die in water. But dragonfly nymphs, mosquito larvae, and water beetles all live in water quite happily!