Unfouling from a sunken ship?

[ambivalentmaybe]

If you're fouled with a ship that sinks, it doesn't seem to possible to unfoul from the sunken vessel and resume moving, unless another ship runs into you, and you successfully unfoul from that one--then you're free to sail. Have I found a bug or a feature? (Disruption, assigning everyone to sail, doesn't make any difference. Turn after turn, it's just 'unfouling attempt failed.')

I'm running what I believe is the latest version of Salvo--it arrived this week in the mail, and I've copied in the 1.5 update files as well. I'm using the Mac OS X version.