Well, the law of salvage wouldn't apply since there's no "peril at sea" involved - the ship and its crew and its cargo are in no imminent danger. They are stuck, but there's no damage or destruction expected to them that would justify salvage. Losses by ship inactivity or blocking the channel are out of scope for salvage, since these are costs to someone else, and salvage law applies when you rescue the property of the ship owner/operator, it refers only to value of ship and cargo and (recently) environmental damage like oil spills (if it would be the liability of the ship operator).