I've been mulling over this film ever since I saw it, and I think the nearest thing I can compare it to are the romantic Borzage silents with Janet Gaynor and Charles Farrell. The intense romanticism, the gorgeous, swooning imagery, the incredible gentleness of the whole thing. If you already like silent films I think "The Shape of Water" will push all the right buttons. It's not like watching a normal film where you follow a spoken narrative in a very literal sense. You feel the story similar to a ballet, with the same intensity of emotion. Films like this rarely get made anymore. At least not for a mass market.
If you're into movies, read on.