Story revolves around two brown otters, one of them is trying to find the moon that is making the reflection in the water. Published sometime prior to 1990. Cover was dark blue and depicted one otter on a cliff near the top of the book the other in the water below the cliff.
Could it be the book, “Ring of Bright Water” ?? See details, here (from Wikipedia):
Maxwell, Gavin (1960). Ring of Bright Water. Illustrated by Peter Scott, Michael Ayrton and Robin McEwen. London: Longmans, Green & Co. Ltd.
Paperback reissue: (1984) ISBN 0-14-003923-6
The book you have mentioned appears to be similar to the one I’m looking for, but unfortunately it’s not the same one. The book I’m looking for was geared towards a fairly young audience and there were no human characters in the story. I do appreciate the help and I apologize because I should’ve included that information in the original description.