Second in the Twins of Petaybee series by Anne McCaffrey... I read the first one a little over a year ago, last March. And I started the third one just as soon as I finished this one since this one ends on a cliff-hanger!
The twins have been sent as ambasadors of a sort from Petaybee to invite their friend's people to come live on Petaybee. Of course there are government/military types that get in the way and make things difficult and there's some new animals/guardians that pose some difficulties as well. And the "deep sea otters" are explained a bit more so we know what they actually are.
By the end of the book everything has gone wrong and no one is where they should be. This obviously made me go hunting for the next book immediately 'cuz I very much needed to know if everything was going to be ok!