The Kraken have spoken : they are getting mildly discomforted by all these bothersome dredging cables and ceaseless activity as mere humans, soaked in greed, dredge up their precious prizes from the Krakens Lair : they feel it only right and proper that these puny yet persistent adventurers face some small risk of awakening the Kraken's Wrath and enduring a modicum of danger as these noble creatures respond to these disturbances : thus it is proposed that a reasonable percentage chance be introduced that a random vessel in the intruding fleet be damaged by loss of a level, or, again randomly, be taken down to the Krakens Lair, their sailors souls to be playthings for the Krakens kindergarten, their timbers to decorate the Krakens Halls, their cannon melted down to make shiny bracelets for the Krakens many arms.
The Kraken feel a 100% chance of such mindless destruction being visited upon these noisome pests is most fair, but will accept the miserable token risk of 5% as being a practical solution to this problem of their tranquillity and peaceful nature being so mistreated.
Edited for spelling : too much Kraken rum... they know how to party...