No Ka Oi (the best) place to go to rent snorkeling gear. Kauai is the most beautiful island in Hawaii with tons of great snorkeling spots and Snorkel Bob's is the place to go to rent your stuff.
They provide maps of different beaches that are prime snorkeling areas. The staff is extremely friendly and fun. They won't hesitate to help you out with your snorkel equipment.
A great place for beginners and experts alike!