Describe the process of pearl hunting or finding?

"Kino had two ropes, one tied to a heavy stone and one to a basket. He stripped off his shirt and trousers and laid his hat in the bottom of the canoe. The water was oily smooth. He took his rock in one hand and his basket in the other, and he slipped feet first over the side and the rock carried him to the bottom. The bubbles rose behind him until the water cleared and he could see. Above, the surface of the water was an undulating mirror of brightness, and he could see the bottoms of the canoes sticking through it.

Kino moved cautiously so that the water would not be obscured with mud or sand. He hooked his foot in the loop on his rock and his hands worked quickly, tearing the oysters loose, some singly, others in clusters. He laid them in his basket. In some places the oysters clung to one another so that they came free in lumps."