One of the best beaches in Maui...or anywhere, though there are no lifeguards. This long sandy beach is a wonderful place to spend the day. There are at least three public entrances, each with showers. My only critique is that there is very little shade on this beach. Otherwise, it's wonderful so bring your own shade if you really need it.
The first entry is at a small parking lot just south of Mana Kai and just north of the Maui Oceanfront Inn. This is also where it may be the most crowded as there are three hotels right here, all of which would direct their guests to this part of the beach.
The second entry is across from a larger public parking lot where Kilohana Dr. meets S. Kihei Rd.
The third entry is another small parking lot at the end of S. Keihei Rd. This one is easy to miss because S. Kihei road splits off from the main drag, which becomes Okolani Dr. S. Kihei Rd at this point becomes a small neighborhood street and runs into a dead end, which is where the parking is. Feel free to gawk at the private beachfront homes here; if you've an extra $8-10 million or so to spend, perhaps you could even buy one!
Have fun, swim with a buddy, and wear lots of sunscreen.