be wary of waves
Disclaimer: Use your brain. If the waves are crashing over the shelf, DO NOT GO DOWN HERE. Even if they aren't crashing, be extremely careful and always be cognizant that just one wave will end you.
This short hike from Highway 340 down to the coast is treacherous when dry and who knows how bad when wet. The trail is equal parts steep, loose gravel, and sharp volcanic rock. It is wise to wear shoes other than flip flops. I managed it ok with Teva's while the wife was good with water shoes.
When you are driving down 340 this is the first major parking area on the left side, after you pass the Nakalele Blowhole parking; roughly 4.5 miles further. There really are two separate options for descending, neither being ideal. We elected to follow the trail to the left, which became much more of a boulder hopping experience (which I enjoyed but others may not). We ascended the right trail, which is more trail than anything but extremely slippery with all the gravel.
Once you make it down to the tide pools, enjoy a swim in the large pool but be wary of waves. Pack out what you packed in and enjoy the animals from a safe distance. There are numerous crabs and fish that inhabit the area.
There is also a less impressive, but equally dangerous, blowhole. DO NOT get too close.
Check out the Triplog.