A fantastical kids' book barely recalled

[arthurstace]

I dimly remember a children's book that's the story of a young girl and her fantastical adventure with some rum coves.

There is, I think, a man in a deep sea diver's suit, a chap who may have been called Captain something and keeps accidentally sewing his legs to his (possibly red) longjohns.

And the tale may end in classic "it was all a dream" style.

But what's the book?

[Patch49]

If you sign up to http://www.abebooks.co.uk/ they have a "Booksleuth" section where you can post plot lines like this and hope it will jog someone's memory.HTH.