Porto de Galinhas is known for its natural coral reef and natural pools. The best time to see it is in the morning during the ebb, when the ocean uncovers the reefs.
In the natural pools you can see colorful fish and actually feed them. You can take a jangada, which is a kind of raft-boat with a sail to the natural pools. The trip costs about R$10 or US$3-5. Be sure to take a mask and a snorkel for snorkeling. It is a fabulous view with fish swimming so close to you.
In the afternoon you can try "beach boogie"--a trip by car, or "beach vehicle." This is a great opportunity to see nearby beaches. It only costs US$15. It is possible to swim only within the area protected by reef--anywhere else there is a dangerously strong current. According to locals, a few people drown every year. Swimming within the protected area is nice and safe and the water is clean.