While technically there are a species or two of sea snakes that have Hawaii included in it's/their range, sightings are very very rare. We'll occasionally get snorkelers saying they saw some kind of sea snake working it's way through the coral. My suspicion is that this is the prime suspect.... what is pictured above is the body of either a Tiger Snake Moray (Scuticaria tigrina) or a Large Spotted Snake Moray (Uropterygius polyspilus), the latter of which I didn't even know existed 'til I opened the book 3 minutes ago to look up the scientific name of what I've always known of as a "Tiger Moray". I think you have to be a bit more of a science guy than I am to readily tell them apart unless you've got a really good shot of their nostrils (I'll have to take a look at my original shots to see if the nostrils above the eyes come in clear enough to differentiate between the two species).
Anyways, it's not totally uncommon to see a view similar to the above of these or other similar species of eels - body only, winding around through coral. The bodies are very tubular, as opposed to the regular morays which have tall dorsal fins, and remind people of snakes. If you are diving you can usually take a bit of a look around the coral head you see the body in and find it's head coming out somewhere. If you've got a camera - be ready, as the head will usually end up in another opening of the coral within seconds. I managed two head shots of this one before it disappeared again.