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Navigating Bridges and Locks

How To Safely Navigate Under Bridges and Through Locks

Just when you think you’ve gotten the basics of nautical navigation and electronic chart management down, along come additional obstacles in the form of locks and bridges. However, rather than being hazards to navigation, bridges and locks assist in moving vessel traffic efficiently and can even be a fun distraction during a voyage so long as you know the basics of safe passage and good protocol.

Navigating Bridges and Locks
Photo by Josh Sorenson from Pexels

Types of Locks and Bridges

A lock is used to raise or lower boats and ships between bodies of water like canals or rivers that lie at different levels. They enable boats to cross uneven terrain and avoid fast-moving or rocky rivers. Locks may be manned by a steward, operated by an electronic remote or managed by the boater manually.

There are many types of bridges including fixed under which you may be able to navigate if the center (or side) span is high enough, swing bridges that pivot horizontally, or draw bridges that open by separating vertically at the center point. Moveable bridges are usually manned by a bridge tender with whom you may communicate via a designated VHF radio channel or by cellphone.

Passing Through Locks

Locks have been built for centuries and function like marine elevators taking vessels up or down a river or canal. The Great Lakes, the Mississippi basin, and the Columbia River in Oregon and Washington states frequently used locks for both commercial and recreational traffic. Europe is full of locks so you may even encounter one during a river charter. Navigation charts should alert you to the location of a lock and what kind it is, which will determine how and when you approach it. Some locks have set schedules while others accommodate traffic on demand.

15 tips to manage locks safely and easily

1. When approaching a lock, you will see either a red or green light. Green means it is safe to enter the lock while red means you must wait. A flashing red light may mean the lock is being operated or is about to open so keep clear.

2. Inform the lockmaster ahead of time your intention to lock through via VHF radio or a cellphone. The channel or number may be listed in a guide for the region. In some cases, you can use the Morse code horn blast to signal the lockmaster. The signal for a lock is the same as that for operating a bridge with one prolonged blast followed by one short blast: –.

3. Once at the lock, moor your vessel or keep station (perhaps with the help of a dynamic positioning system) in the designated waiting area, sufficiently away from the lock opening. Boats already locking through will need space to maneuver out of the gates. There may be current in the immediate vicinity of the gate so keep clear.

4. Wait your turn in the queue. If there are vessels ahead of you, don’t drift about in the way. Follow the lockmaster’s directions or just keep clear until allowed to approach. Commercial vessels usually take priority but the lockmaster may load up a large lock for maximum efficiency and will let you know where and when to go.

5. Hang fenders on both sides of your vessel and prepare lines the length of which will depend on the size of the lock and your boat but usually at least 50 feet.

6. Enter the lock slowly, avoiding creating a wake. Position yourself well forward in the lock or wherever the steward designates.

7. Secure the vessel with lines to bollards, hooks or cleats in or on the lock walls. Actively man each line, loosening the lines when locking down and tightening them when locking up. Never cleat a line and leave it unattended or you risk capsizing or a tearing out a ship’s cleat. Best practices include cleating the line to the vessel, draping it around a bollard or ring and manning the loose or bitter end.

8. Turn engine(s) off.

9. Do not smoke.

10. Use the designated ladders on the lock walls if you need to operate the lock yourself, converse with the steward or hook your lines over cleats at the top of the wall. These ladders spend half their time underwater and they are usually slick or covered with marine growth so mind your hands and feet when using them. Gloves may help.

11. As the lock fills or drains, a current will move the boat about. Take care not to cause damage by hitting other vessels or the walls of the lock.

12. You may want to keep a boathook handy to help push away from the wall or other boats as the water level changes or to help a line go over a hard-to-reach bollard.

13. Once the gates open and you get the signal from either a green light in the lock or the steward, you may proceed out of the lock.

14. Motor slowly. Don’t engage your prop(s) until your lines are clear of the water.

15. Anticipate waiting traffic on the other side and maneuver carefully.

Navigating Under Bridges

Bridges are common on both coasts and on inland waterways such as the ICW. Information regarding bridge location, type, schedules and communication preferences can usually be found on navigation charts or in piloting and cruising guidebooks. Check the USCG Local Notice to Mariners for changes, construction or temporary bridge inoperability.

For moveable bridges, know that it’s illegal to cause an unnecessary bridge opening per the US Code, Title 33. Penalties can be high. Some bridges open automatically on schedule while others are manned and open on request as terrestrial traffic allows. Your chart should provide information on how to communicate with the bridge tender if there is one.

15 tips to navigate bridges safely and easily

1. Know the name of the bridge you’re approaching and hail it on the proper VHF channel. In certain areas, multiple bridges may be within hailing distance on the same channel so address the bridge by name.

2. Check schedules in a guidebook or by calling the bridge ahead of time. This may impact how fast you travel. There’s no need to hurry just to wait for opening times but you shouldn’t dawdle if the bridge only opens hourly and you have the ability and speed to make the schedule.

3. If it is a fixed bridge, know your own air draft or vertical clearance including various high-mounted antennas. Check the tide. At high tide, you may not be able to pass under a fixed bridge. At low tide, you may not be able to clear your waterline draft. Tide boards near the bridge indicate bridge clearance for a given state of tide.

4. Fixed bridges may have markings as to which span you must pass under. These may be color markings on the bridge itself during the day or red/green lights at night. Smaller vessels may be able to pass under lower spans but beware of submerged obstacles or pilings anywhere outside of the designated span.

5. Inform the bridge tender ahead of time of your intention to pass a moveable bridge. Use VHF radio (usually channel 9, 13 or the hailing channel 16). In some cases you may also use a cellphone or horn blasts: –.

6. Moor your vessel or keep station (perhaps with the help of a dynamic positioning system) in the designated waiting area, sufficiently away from the bridge. Some bridges will have red and green lights signaling whether or not they are ready for through traffic.

7. Wait your turn in the queue. If there are vessels ahead of you, don’t drift about in the way. Notify the tender of your intent to pass even if other boats are waiting so the bridge doesn’t close on you unexpectedly.

8. Anticipate eddies or currents around a bridge especially in a restricted channel. Keep in mind your windage and what affect it will have when passing a bridge in gusty conditions. Also watch for small boat traffic coming from the opposing side or vessels fishing near pilings.

9. When clear, navigate with acceptable speed – slow enough to be safe but fast enough to avoid making road traffic above wait unnecessarily.

10. Rules of the Road are important. Give way to oncoming traffic that is moving down river/current. Those vessels have less control than the ones moving up current. Also give way to vessels restricted in their ability to maneuver either due to size, draft or other circumstances such as a tug and tow.

11. Sailboats should motor through under auxiliary power if so equipped. Sails can obstruct the view of the bridge and oncoming traffic and wind shifts and calms can be unpredictable under a bridge.

12. Do not proceed until a bridge is completely opened.

13. Do not overtake other boats while passing under a bridge. Pass in a single file line, especially if there is oncoming traffic or boats on the other side, which you can’t see.

14. Five short blasts signal a problem, danger or emergency. This may include a boat losing power while passing or the bridge tender needing to close the bridge for emergency or rescue traffic above. This signal may be sounded by the bridgeman or the passing boats.

15. After passing under a bridge, navigate to starboard if there is sufficient room and water depth and pass other vessels port-to-port as is customary.

Bridges and locks can be a welcome diversion and good teaching moment for everyone aboard. Learn the proper etiquette for passing through or under each and then enjoy the journey.

Written by Zuzana Prochazka

Written by: Zuzana Prochazka

Zuzana Prochazka is a writer and photographer who freelances for a dozen boating magazines and websites. A USCG 100 Ton Master, Zuzana has cruised, chartered and skippered flotillas in many parts of the world and serves as a presenter on charter destinations and topics. She is the Chair of the New Product Awards committee, judging innovative boats and gear at NMMA and NMEA shows, and currently serves as immediate past president of Boating Writers International. She contributes to and, and also blogs regularly on her boat review site,