I won’t be there until July, but I have a recommendation for you. My favorite shore dive on Kauai is Tunnels on the North Shore. But to dive there I highly recommend using a guide. We typically do this with Fathom Five Divers, who bring all the gear and set it up on the beach for you. The tunnels running under the main snorkel reef are very cool. I’ve seen everything from large reef sharks to spanish dancer nudibanch’s there. For the second dive they typically take you to the outer reef for a close up turtle cleaning station. I did this shore dive on my own the first time and didn’t see sht. Well worth the money. But if budget is a serious concern I have always had an easy time with a decent dive at Koloa Landing on the South Shore. Easy entry and exit thanks to a boat ramp. Pretty straight forward dives there which don’t necessarily need a guide.