Final answer:
Diving bell spiders obtain air using gills. They bring back a bubble of air from the surface and deposit it into a silk air tank called a 'diving bell'. The diving bell acts as a gill, extracting oxygen from the water.
Step-by-step explanation:
Diving bell spiders obtain air using gills. These spiders, also known as aquatic spiders, have a unique way of breathing underwater. They leave their underwater web and bring back a bubble of air from the surface, which they deposit into a silk air tank called a 'diving bell.' The diving bell acts as a gill, extracting oxygen from the water and allowing the spider to stay underwater for up to 24 hours.