But as you introduced thought of, the otters would possibly be as subject to getting Ray Bees as their river cousins, if not for living most of their lives not on dry land (they don't 'haul out' much). So you did have a point, but one I didn't catch.
From what I've read about sea otters, they became sea-going otters in the first place in avoiding land predators -- or so the not-unreasonably story goes.
I do recall however, of having Fish & Game biologist approach myself and others with the "news" that sea otters had been sighted in the Estero Bay area (it took a few more years for them to make waters of Morro Bay itself included as regular home).
I thought to myself (and told them) when they excitedly told us the "news" -- reallY? "Ok, I've been looking at them for the last two years...how long has this been a revelation among CDF&G" ...NMFS and maybe NOAA? "Ya'll could tell me that, but I already know the first part."
Besides...just who was it that buried the old mentions (that USED TO exist) of plan to transplant a few animals from up North (trapped in Alaska I think was how it did occur) and drop them off somewhere near Pt. Sur? The plausible deniability excuse is there was a plan to diversify an isolated population with fresh genetics from elsewhere -- but it did not occur -- or if it did, it went according to plan --- simply adding to genetic pool rather than be fully re-introduction into a "void", or even outright introduction.
Whichever way that had truly went, for a few decades (maybe 5?) there was "an isolated colony" of the critters along what we call the Big Sur Coast. Those eventually expanded their range.
As the old-time fisherman tell it (those in the know who'd spent their lives fishing those areas and communicating with others whom did so) otters been transplanted from up North after having allegedly been wiped out some time near, or right before turn of the 20th century --if they'd been there at all prior to Spaniards, and traders of other nationalities arriving willing to pay money for sea mammal hides.
Had they existed there at all by the time Europeans arrived, the animals would not be too difficult to wipe out using canoes, bows, and spears.
One tribe of Big Sur area Indians in particular had truly big and damned good canoes -- the best they'd ever seen according to European/American ship captains, as can be read about in literature touching upon the subject.
IIRC, those particular 'native Americans' were also markedly differing in appearance than other tribes -- most of which they did not get along with very well. They lived near to where Nepenthe is now, I think I'm remembering...
I cannot recall that tribe's exact name, but the literature I'd encountered on the subject was from among oldest written European language records pertaining to the subject, which had as included among it's focus, efforts of one, or a few men to conduct interviews of the oldest living Indians (using translators) asking them of what they knew of their own tribes past histories. I'm pretty sure there is no mention in those sources of "sea" otters fwiw. If I come across the information (found online) again, I'll keep an eye out for it -- but I seem to remember having been looking for that as I went along, back when I'd first encountered the literature.