Bill,
This is nothing new. Boat/US provided all of their customers a "towing
Contract" so their customers would not get stuck with a "salvage"
claim, when they thought they were agreeing to a tow.

When they sent me the form they listed a number of examples of how
towing companies have legally enforced a "salvage claim" for situations
where the owner thought he was contradting for a tow.

It is not as cut and dry as it would appear. Here is an article
boat/us wrote on this subject.
http://www.boatus.com/towing/guide/salvage/towsal.asp

The tow operator can say, he believes that his work of moving the boat
not only saved the boat but protected the enviroment. He can also say
his work allowed the firefighters to return to their real job of
fighting the fire which protected the enviroment further.

Don't get me wrong, I think the tow operator is a shyster, but I will
give 100 to 1 odds he will not be charged with filing a frivalous law
suit or salvage claim.