Heading for east coast. We had 2 locks today. Going to Cape Canaveral we had a lock through from the Banana River to the Atlantic. It was lock doors that open, you go in and tie off to the side while they close those doors and open the East set of doors. No water height change . So needed to know why so I looked it up. It reduces tidal-current velocity in the Harbor, prevents hurricane tides into the river and salt water intrusion. While inside we were entertained by about 4 or 5 Manatees  enjoying a little playful time.