The counter pollution response at sea - air and surface operations. The counter pollution response on shore. The incident may have no fixed location. And, if it does not, it may be difficult to predict changes in that location. Contrary to the land based situation, the actions of many of those involved can create entirely new and different problems for others involved.
Obvious examples are a decision to trans-ship cargo or to beach the vessel.
Another fundamental difference is that salvage involves a commercial contract between the owner of the vessel and the salvor. To the extent that harbour authorities want to minimise pollution of their harbours their interest coincides with that of the Secretary of State. In different situations there will be different levels of command to be exercised consistently with, and in furtherance of, the plans and intentions of the person in control. In all cases there will be salvors and owners with command over their own vessels, employees and assets. There may be a harbour authority with control and command over what happens within its area.