The fresh water entering Florida Bay from the Everglades creates ideal conditions for vast beds of turtle grass and algae formations that foster animal life in the bay. Sea turtles and manatees (Trichechus manatus latirostris) eat the grass, while invertebrates such as worms, clams, and other mollusks consume algae formations and microscopic plankton.[75] Female sea turtles return annually to nest on the shore, and manatees spend the winter months in the warmer water of the bay. The Calusa Indians had various uses for shells of marine invertebrates, due to the lack of dense rock with which to make tools. They used the horse conch (Triplofusus papillosus), left-handed whelk (Sinistrofulgur), and the Florida crown conch (Melongena corona) as drinking vessels, picks, hammers, knives and awls.[76]