Spring dived for
Puna is a spring and luʻu is to dive. Fresh water rises from springs on the sea floor just offshore, and people dived with gourds to fill them from the freshwater plume before it mixed with salt.
The name is a set of instructions compressed into two words: there is fresh water here, and you have to go under for it.
Black sand and honu
The sand is basalt, shattered when lava met the sea. Honu, green sea turtles, bask on the beach in numbers — they are protected, and the ten-foot rule applies.