How do seabirds get caught in fishing nets?

Mammals are usually caught in nets, but long line fishing catches more than just target species of fish. Sharks, turtles and seabirds are all attracted to the bait on the lines of long line fishing. Seabirds get caught on the lines and drown.

by diving into the water to get fish that happen to be in fishing nets

Explanation:

seabirds dive for their food (fish) and they may not see the fishing net. So they dive so they can catch the fish and they get caught in the fishing net