A reader, Lily, sent an e-mail with a picture and a question about some pipipi, snails also called nerites, she saw at Kawaikui Beach near Aina Haina.

“;I always thought they stayed on rocks where the waves hit,”; she wrote, “;but these were spread out on the bottom [underwater] on the sand and rocks. I thought that might be normal for the area but figured it wouldn't hurt to ask.”;

It didn't hurt to ask. When I didn't know the answer to Lily's question, I began searching for information about these native snails and found, as usual, that they're remarkable little creatures.

Pipipi are well named. The Hawaiian word means small and close together, and that's how most of these half-inch-long snails spend their days—crowded together under ledges or in depressions of Hawaii's rocky shorelines.

The scientific name of this family, Neritidae, comes from the Greek sea god, Nereus, and from that comes the common English name nerite. (Scientists also used this god's name in the term neritic waters, which describes the ocean from the low tide line to about 600 feet deep, or the continental shelf, where most marine life is found.)

Members of the nerite family are the most widespread and abundant of all snails, ranging throughout the world's tropics and subtropics from the highest splash zone to 3 feet below water.

Of the nine species native to Hawaii waters, all have versatile gills that can extract oxygen from sea, brackish and fresh water. It's plain to see they can also take it from the air.

Three kinds of nerites live in Hawaii's fresh or brackish streams, and there lay their eggs. After hatching, the youngsters, in larval form, wash into the ocean where they mature. This takes from a few months to a year depending on the species.

The young adults then hike back to their streams to live and reproduce.

Of the six species of strictly marine nerites in Hawaii, two are common. The most abundant are the half-inch-long pipipi that Lily referred to. These snails' shells are black and covered with spiral grooves.

Most pipipi spend their time on rocks between the high and low tides, but they can live above and below the tide lines, too. Pipipi sometimes live underwater on shallow rocky bottoms and inside tide pools.

When they venture above the high-tide line, they stay within the splash zone. Some even hang onto tree branches hanging low over the water.

Location for marine nerites isn't about breathing. It's about algae. During the day, these grazers snuggle together and stay put, but at night they move around eating algae growing in their neighborhood.

One larger nerites species, with the Hawaiian name kupee, grows to an inch long and lives under the sand during the day, emerging at night to graze.

Ancient Hawaiians prized kupee shells using them in bracelets and necklaces. These thick gray shells bear white, yellow, pink, orange, red or black spots.

Hawaiians ate all species of these snails, sometimes raw, sometimes heating them, then plucking the snail from its shell with a sharp stick.

I've seen pipipi on shallow ocean floors countless times, but I didn't know why they did that. Thanks to Lily, I do now. It's not only normal for Kawaikui Beach; it's normal for pipipi. They lounge around underwater because they can.