I went snorkeling there today. It was fairly low tide and a couple feet of swell.
There is indeed a nice wide sand channel about 200' east (towards pali) of the parking lot. The entry is a little tricky as there are some awash rocks between shore and the beginning of the channel, but you can go around either side. The viz was pretty bad, but I swam on out well beyond the breakers and the channel goes all the way, with just a couple of coral heads. The channel was obvious from shore because the waves came right on in, while on either side they broke while well offshore. To stay in the channel I kept a large distinctive driftwood tree centered in the valley or lined up with the peak at the right back side of the valley. The driftwood is more or less in the middle of 7 or 8 segments of Jersey barrier 200' towards the pali from the parking lot. (It seems to have been around a while, and is even on the google street view). Start point, from google maps is 20.79454N, 156.581W. (Just copy and paste into Google Maps and a marker will pop up there).
I also found the channel described by spoolin01. It is in line with the cut through the dunes that is closest to the parking lot. The channel is clearly visible as a whiter zone that leads straight out. Entry was nice. Entry is at 20.79526N, 156.58391W. The viz appeared to be better than in the sand channel that I used. As you go out the channel, be sure to note some objects that line up so that you can find the channel again.
The Maui Dive Shop boat came by and dropped divers off at about 10:45AM. Their drop point was offshore from the roadside picnic tables just to the Lahaina side (west) of the entrance to the parking lot. They were dropped off a bit to the east of the channel described by spoolin01. The dropoff point was not very far offshore. It was just 100 or 200' beyond the surf line, and shoreward of the shallow water/deep water color change that is very visible. Somewhere around 20.7924N, 156.5833W
This beach is a popular surfing and standup board spot. The waves break nicely even with small swells. Unfortunately, that makes it kind of nasty if you end up on top of shallow coral.
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It's possible to do it from shore, but it could get really ugly if you end up on top of the shallow coral with breaking waves on top of you. It was nice exploring, but I think I'll stick with boats for this dive site.