Underwater cameraman Scott Cassell with a Humboldt squid in Baja's Sea of Cortez.
Cassell, photographed in Santa Rosalía, Mexico, says his first Humboldt encounter was like "being in a barroom brawl."
Humboldt expert William Gilly, in his California lab.
Gilly examines a dead squid.
Santa Rosalía fisherman Rafael Garibaldi.
A Humboldt approaches the boat.