One spider spends its entire life underwater, breathing from a bubble it wove itself
The diving bell spider builds a dome-shaped web between underwater plants and fills it with air carried down from the surface on its hairy abdomen, creating a silk 'diving bell' it can live, hunt, molt and even mate inside. The bubble acts like a gill, pulling in dissolved oxygen from the surrounding water as it's used up. It's the only spider species known to spend essentially its whole life submerged.