Several years ago (2019), I took my kids to Maui, and we ended up driving to the NW shore of the island (near Slaughterhouse Beach / Fleming Beach)[1], and we continued on to eventually park on the side of the road next to a nature reserve. We ended up walking through the reserve to a very rocky beach to snorkel.
It was very random in that we didn't know where we were going, nor where we would end up.
Up until then, we had only ever snorkeled on sandy, shallow beaches where the water was cloudy and there weren't a lot of fish (and little to no coral).
This place we found in Maui was a wonderland. It was like something out of a BBC nature documentary. It was rocky and became deep right away (so the water was clear). And it was a protected bay, so the currents were a minimum. The fish, coral, and anemones were simply spectacular and it was a memory that's been permanently etched into my mind.
Since then, I've been on the look-out for a similar experience. We went to Kauai (2022), but only found sandy beaches[2] (and the rip tides were just wicked).
And even on our visit to The Big Island, we began at Nanuku Inlet and Puako Bay (on the reef part), and those were fine (and sometimes even great), but not like Maui.
But then we found it: Keylakekua Bay. We hiked down the two mile trail to the Captain Cook monument[3] and jumped into the water. It was spectacular. It was otherworldly. Because I had repurposed an old trail-running camera to use for snorkeling[4], we had an underwater camera with us.
My claim, which I'm sticking with, is that if everybody could see what's below the surface at places like Keylakekua Bay, everyone would become (1) and environmentalist and (2) would join a "Keep Plastic Out of the Ocean" organization, e.g.: The Ocean Cleanup Project.
Hawaii is a national treasure (and arguably also a global treasure).
Here are my favorite snorkeling photos. They're mostly from Keylakekua Bay, but there are some from Puako Bay (the reef section) and maybe even one from Nanuku Inlet.
Incidentally, here's a list of places we visited while on the Island: