It was about this inspector guy (I think he was an otter) and his niece and nephew (or kids, I cant remember)
it was basically a series of books that labeled everything on the pages. the one I read was about a sunken treasure. the two pages I remember most was one in like a bait and tackle shop. On this page it had things labeled like a fishing net, compass, fishing poles etc. on another they were sailing through rough seas and there were alot of whales, like a narwhal, blue whale, flying fish, etc.. again everything was identified with a word right next to it.
anyway I hope thats clear enough, I might try to see if my grandfather might still have it but I doubt it, hopefully someone knows what Im talking about, I cant find anything on it on google.