Loggerhead sea turtles are the largest of the hard-shelled sea turtles. They have large heads, strong jaws and a reddish-brown shell, and they can weigh up to 1,000 pounds. On average, they’re about 250 pounds though. As far as turtles go, the sea turtles are fast, swimming up to 15 miles per hour. In fact, female loggerheads will sometimes swim thousands of miles to lay her eggs in the exact place that she was born.