If you have more time, you can visit the Thiruvananthapuram Zoo, which is located near the Napier Museum and Art Gallery. The zoo is open from 9:00AM to 5:30PM and the entry fee is INR 40 for Indians and INR 80 for foreigners. If you have less time, you can skip Poovar Island and directly head to Kovalam Beach. Do carry sunscreen, hats, and sunglasses as the sun can be quite harsh. Also, carry sufficient water and some snacks for the trip.