Refloating a Grounded Vessel
By Gus Marchetti, Salvage master. Reviewed by Amanda McCallister, editor.
Marine Salvage & Recovery | Hull & Bottom Cleaning I was on the bridge of the M/V Osprey at 0300 when she went hard over – a sandbar off the Georgia coast, we'd hit it at full sea speed, call it 14 knots. The forepeak was taking water and the bow was sitting up, I'd say three meters high, like a dolphin at play. That scene has played out more times than I count. Refloating a grounded vessel is not heroics. It's a dirty, wet, stubborn arithmetic problem. You've got to know how much weight the ship carries, how much buoyancy she's lost, and what the bottom will tolerate. In this post, I'll walk you through the steps that have worked for me across 22 years of salvage. You won't find magic tricks here – just the same physics that every tugboat captain and salvage master has used for a century.
Start With a Hard Look at the Problem
The first move is always to keep steady. Get a surveyor over the side with a multibeam echo sounder to map the bottom. We need to know if the hull is resting on a sand ridge, a rock ledge, or a mud bank. Sand and mud give up the ship easier than rock. And we need to know where the hull is damaged – if the bottom is already breached, pulling can sink you. Then check the tide. Tide is your best friend and your only clock. In the Panamanian ports, you can get five or six feet. In the Bay of Fundy, you get forty. That's the difference between a weekend job and a month-long circus. You need the tide table, the weather forecast, and the local knowledge of how the bottom shifts. A quick digression: an old towboat captain I once worked with believed in pouring sandbags around the hull's keel to stop the water scouring under it. That can actually work on hard, firm bottoms. On soft mud, it's just extra work. Depends on the plant.
Lighten the Ship
You can't just winch her off. Every tonne you leave aboard presses the hull into the bottom. So you start taking weight off. First, you transfer fuel and ballast from the tanks on the grounded side to the far side. A big vessel can shift thousands of tonnes of liquid ballast and change her draft by half a meter. That's often enough to free her. If not, you start discharging cargo. This is where salvage gets physical. We've used cranes, grabs, air bags, vacuum loaders, and a few times helicopters to lift bags of rice out of a flooded hold. I remember a grain carrier in the Suez – we had to move 4,000 tonnes of barley off with a self-propelled beach hopper. That took three days. Roughly speaking, every 1,000 tonnes you take off drops the draft by a quarter of a meter on a 30,000 DWT bulker. Depends on the waterplane area, but that's the ballpark. Anyway, you get the idea.
Pull With Tugs and Anchors
Once the ship has a draft that matches the water depth, you can start the pulling. Tugs are the usual answer. We set a messenger line, then a 64mm wire rope from the ship to the tug. A modern Z-drive tug like a Damen ASD 2810 will put out 60 to 80 tonnes of bollard pull. But if the hull is still stuck by suction, you won't budge her. The trick is to take advantage of the ship's own anchor. Deploy the opposite anchor off to the side and deep water, then heave with the anchor winch. This causes the ship to pivot on her bow and can break the suction. Combine that with tugs pulling at 15 degrees off the centerline, and you get a gentle rocking action. Also, always time your heave with the rising tide. Wait for high water slack, when the current is minimal and the ship has the maximum water under her. Then put the engines astern, turn the wheel, and call it done.
The Refloat and Aftermath
When she slides off, it's not a big crash – it's a sudden, quiet surge forward. Water wets the hull, and the deck leans back to normal. Then comes the inspection. You check the holds, the engine room, the shaft alley, and the rudder. Any ruptured tanks need to be pumped and sealed. Then you put the vessel under tow or let her navigate to a repair yard. But the job ends with a briefing. I always tell the crew: just because you got her off, it doesn't mean the trouble is over. The next 24 hours are for cautious seamanship, not for celebrating. A common mistake I see in younger salvers is they stop pulling the moment she's free. You always have to be ready for her to re-aground if you stop too soon. So you keep the tugs hooked on for another hull's length at least. Better safe than stuck again.
Frequently Asked Questions
How long does a refloating operation take? It depends on the ship, the cause, and the weather. A simple tide-assisted refloat on a sandy bottom can happen in a few hours. Cargo discharge on a big bulker can take a week or more. Call it typical 2-5 days. Can a grounded vessel refloat without tugs? Yes, if you have a working anchor and winch, enough water under the keel at high tide, and a healthy engine. Shift ballast, heave on the anchor, and run astern. But it's risky. Better to have a tug standing by even if you don't use it. What's the most common mistake in refloating? Pulling before lightening. If you try to tug a fully loaded ship off a sand bar, you might pull the bitts off the deck or permanently deform the hull. Always reduce deadweight first. How much bollard pull do you need? No fixed number. A rule of thumb from the old days is 1 tonne of bollard pull for every 10 DWT, but that's only if the hull is already free. In practice, you use the anchor and the ship's own power, and tugs are just an assist. Better to get a naval architect to calculate the forces for a specific case.