Port Mayaca Lock and Dam, Navigation lock and water control dam at Lake Okeechobee, Florida.

Port Mayaca Lock and Dam is a navigation lock and water control facility at Lake Okeechobee that allows boats to move between different water levels. The lock chamber is 56 feet (17 meters) wide and 400 feet (122 meters) long, with steel sector gates that open to permit passage.

The Port Mayaca Lock and Dam was built as part of the Okeechobee Waterway on the St. Lucie Canal, next to U.S. Routes 441 and 98 in Martin County, Florida. Its construction cost $13.1 million. It was created to raise the lake's water level, keeping fresh water for agriculture, city supply and navigation, and to regulate flood-control water into the Everglades during hurricane season.

Boats announce themselves to the lock on Marine VHF radio channel 13, the working language of the Okeechobee Waterway. The lock sits beside US 441 and US 98 near Port Mayaca, so passing traffic can watch the steel sector gates swing open. When polluted lake water is released into the C-44 St. Lucie Canal, it can spawn algae blooms whose cyanotoxins cause nausea, rashes and breathing trouble.

The lock is open daily from 7:00am to 5:00pm, hours that took effect on 1 April 2015. Boaters should call on Marine VHF radio channel 13 to reach the lock. The structure sits beside U.S. Route 441 and U.S. Route 98 near Port Mayaca in Martin County.

The facility includes a spillway system with four vertical lift gates that can manage enormous water flows. This technical design allows it to handle rapid water level changes while keeping the system safe.