From National Geographic:

The Shark Men are headed back to the waters where they have successfully caught and tagged almost a dozen sharks; Guadalupe Island. Dr. Domeier almost has enough data to support his theory about great whites mating at the island. But still needs a few more blood samples, his primary target; adult females. No matter how familiar the waters are nothing goes off without a hitch for this team.

The latest episode “As Big As A Boat” premieres this Sunday (05/01) at 10pm ET/PT on the National Geographic Channel.