The deep sea angler fish is a very fascinating creature. In the dark environment of the deep sea, the fish uses lures filled with bacteria that create light and attract prey.  Furthermore, the female, which is substantially larger than the male, uses flashing lures to attract a mate.  The male will then attach itself to the female and becomes absorbed into her body.

For more information on the angler fish, you may be interested in the BBC documentary, The Blue Planet – Seas of Life (Part 2).