Your book made the difference between a good vacation and a great Hawaiian experience. The walk down will take about 7 minutes, and it is pretty much straight down. As the path makes the last sharp plunge, you can see a magnificent stretch of sand and a shining turquoise sea. In rainy times, this enormous beach may be partly covered by a lagoon fed by a stream winding down behine the beach. Towards the right you'll see the Kilauea lighthouse.
Swimming is risky.
Surf can rough, and currents strong and unpredictable. In winter, this beach, enormous as it is, can disappear almost entirely under huge crashing waves. Instead of swimming, walk along the water, hunt for shells, and forget everything but the feel of wet sand between your toes. Bring a picnic lunch from Farmer's Market Deli in Kilauea and lots of fresh water. The walk back up will take about 10 minutes, just long enough to readjust to the world you left behind.