Strait of Hormuz: How months of closure creates challenges for ships

Published 25 June 2026 · world

Celebrating the MoU between Iran and the U.S., President Donald Trump said it was time to start the engines and let the oil flow. Yet

Celebrating the MoU between Iran and the U.S., President Donald Trump said it was time to start the engines and let the oil flow. Yet one of the biggest challenges facing shipowners and crews lies largely out of sight, beneath the waterline. “Ships are not designed to remain indefinitely idle. Even when stationary, a ship remains a continuously living industrial system requiring maintenance, preservation and regulatory oversight,” says Ajithkumar Sukumaran, retired Additional Director General of Shipping. For vessels that have spent prolonged periods at anchor, restarting operations is not as simple as weighing anchor and proceeding to sea. Extended waiting periods create a chain of technical, regulatory and human-factor challenges that can take weeks or even months to fully address. Among the most immediate concerns is underwater biofouling — the accumulation of marine organisms on hull surfaces, propellers and seawater intake systems. In the warm waters of the Gulf, where sea temperatures can remain high for much of the year, marine growth can develop rapidly. What begins as a thin biological film can soon evolve into layers of algae, barnacles and other organisms that significantly affect vessel performance. “Warmer regions of Persian Gulf areas promote rapid growth of marine organisms on the hull surfaces, both on the open hull and underwater,” says Priyatham Ramidi, P&I Marine Surveyor. The consequences extend far beyond appearance. Ship hulls are shaped and designed to reduce water resistance. A fouled hull increases this resistance, forcing engines to work harder to maintain speed. That means a loss of efficiency. Even moderate levels of fouling can lead to substantial increases in fuel consumption, while severe fouling can dramatically reduce propulsion efficiency. For large tankers and container vessels, the additional fuel costs can run into hundreds of thousands of dollars over the course of a trading cycle. The problem becomes particularly acute after prolonged anchorage. Anti-fouling coatings used on modern vessels are generally designed to perform best when ships are moving regularly through the water. When vessels remain stationary for weeks or months, these protective systems become less effective and marine growth accelerates.

Propellers are especially vulnerable. Even relatively small accumulations of marine organisms on propeller blades can disrupt water flow, reduce thrust and increase vibration. Rudders, thruster tunnels and azimuth propulsion units may experience similar effects. By the time vessels are ready to resume trading, some may require underwater inspections and cleaning operations before they can return to efficient service. This may well present a business opportunity for such underwater cleaning services offered by Indians along our coast. The majority of the stranded ships are eastbound and they will head out and hug the Indian coast before turning east below Sri Lanka. And they can drift in the sea for a day or more to get the cleaning done. Sea chests present another concern. These recessed compartments on the ship’s hull are openings into the sea. Through these, seawater is sucked in by pumps and used for cooling in various machineries all over the ship. Extended periods at anchor increase the risk of marine growth accumulating around sea chest gratings at these openings. Partial blockages can reduce cooling efficiency, potentially leading to overheating of critical machinery once operational demands increase. For engineers preparing a vessel for departure, checking the condition of seawater systems becomes a priority. Strainers, filters, pumps and coolers must be inspected to ensure adequate flow rates. In some cases, underwater inspections may be required to determine the extent of fouling before a vessel can safely resume operations. Yet underwater growth is only one part of a much larger picture. The prolonged waiting period effectively creates a form of unintended lay-up. Although ships may remain technically operational, many systems are forced into conditions for which they were not originally designed. Main propulsion engines, for example, benefit from regular operation. Long periods of inactivity can increase the risk of cylinder liner corrosion, sticking piston rings and deterioration of lubrication films. Fuel systems may also be affected. Reduced fuel consumption and extended storage periods can contribute to sludge formation and contamination in fuel tanks and pipelines, says Mr. Sukumaran. Auxiliary engines and generators face a different challenge, he adds.