Crabby Daddy's on Rayford Road near The Woodlands is very good for seafood; fun atmosphere, too. Bluewater Seafood on Fm 2920 is pretty good, too.There is one seafood restaurant in Tomball I have seen - Za Za Za Seafood. Never been, but you may want to 'Google' it for more info.
Babin's at Willowbrook Mall gets good reviews. I went there once and it was very good. Normally I wouldn't suggest a Fertitta restaurant, but this one seems to be the exception.