Sea turtles have different diets, depending on the species. Green sea turtles are herbivorous, and feed mainly on algae and sea grasses. Hawksbill turtles feed mostly on sponges while Kemp's ridley sea turtle eat crabs and other crustaceans. Leatherbacks, the largest sea turtle, feed primarily on jellyfish. This can cause problems because floating plastic bags are easily mistaken for jellyfish by the turtles, and can cause mortality.
Loggerheads eat crabs, jellyfish, and molluscs.
Other sea turtle have similar diets. Sea turtles can dive for as long as 2 hours. Not much is known about the ages that sea turtles can attain. It is assumed that once sea turtles reach sexual maturity, they are reproductively active for around 30 years. Seeing as some species don't reach sexual maturity for 50 years, an 80 year lifespan seems reasonable.