What are three characteristics allow fish to live in the water?

1. Gills: Fish have gills that allow them to extract oxygen from the water. Gills are made up of thin filaments that are covered in tiny blood vessels. As water passes over the gills, the oxygen in the water diffuses into the blood vessels and is carried throughout the fish's body.

2. Fins: Fish have fins that help them to move and maintain their balance in the water. Fins are made of thin, flexible rays that are supported by cartilage or bone. Different types of fish have different types of fins, but all fish have at least one pair of pectoral fins (located on the sides of the body) and one pair of pelvic fins (located on the underside of the body). Some fish also have a dorsal fin (located on the back), an anal fin (located on the underside of the body near the tail), and a caudal fin (located at the end of the tail).

3. Swim bladder: Most fish have a swim bladder, which is a gas-filled sac that helps them to maintain their buoyancy. The swim bladder is located in the dorsal part of the fish's body, and it can be inflated or deflated to change the fish's overall density. When the swim bladder is inflated, the fish is more buoyant and can stay suspended in the water without having to swim constantly. When the swim bladder is deflated, the fish is less buoyant and will sink to the bottom of the water.