Just 6km south of Kovalam, this incredible conservation and research trust is a fascinating peek into the reptile world. Founded by croc/snake-expert Romulus Whitaker, the bank has thousands of reptiles, including 17 of the world's 23 species of crocodilian (crocodiles and similar creatures), and does crucial work in maintaining genetic reserves of these animals, several of which are endangered. There's also a snake venom extraction centre (open 10am to 1pm and 2pm to 5pm), where you can watch scary serpents being milked.
There are openings for volunteers at the Crocodile Bank (minimum two weeks).