Gill chambers (in crabs)
Crabs have gill chambers to store water, allowing them to take in dissolved oxygen from the water through their gills even while they are on land.
Marine mammals are capable of staying underwater for long periods of time before surfacing to take in air. Observe the different structural and behavioural adaptations that allow them to do so!
Carrying water bubbles (water beetles)
Similar to how we carry an oxygen tank when we dive in water for long periods of time, the water beetle carries its own bubble of air when it dives underwater to search for food.