Final answer:
The swim bladder in fish and the ballast tanks in submarines both regulate buoyancy. Fish can adjust gas volume in their swim bladder, while submarines manage water in ballast tanks to sink or float. Some fish lack swim bladders due to different evolutionary adaptations.
Step-by-step explanation:
The swim bladder of a fish and the ballast tanks of a submarine serve similar functions. Both structures are used to control buoyancy, allowing the fish or submarine to maintain a desired depth in the water without expending energy. The swim bladder is a gas-filled organ that fish can adjust by varying the amount of gas it contains, helping the fish to rise or sink in the water column. Submarines use ballast tanks to manage buoyancy by taking in water to sink or releasing water to rise, much like how the swim bladder works in bony fishes. Not all fish have swim bladders; some, including many bottom dwellers or fast swimmers, have evolved other mechanisms to control their buoyancy. As for submarines, they have been known to inadvertently transport fish in their ballast tanks, leading to species being introduced to non-native environments.