I lived in Houston for roughly half of my life and kept my boat at Waterford Marina in Kemah. Although we no longer live there, I have kept up with the Kemah/Seabrook restaurants.
The Kemah/Seabrook waterfront restaurants have had a long and checkered life. Jimmy Walkers (now renamed Landry's Seafood, a part of the Landry's mélange of Kemah Boardwald restaurants) has always been the nicest and maybe the best. Other restaurants on the Kemah side downstream of the bridge, have all been purchased by the Landry's group. While we can bemoan the demise of the independent fish house, Landry's still has some nice restaurants in their group. I like the Flying Duthman for a more casual environment than Landry's/Jimmy Walkers. There is an upstairs (more formal) and a downstairs (not air conditioned and more casual).
But across the channel on the Seabrook side are where the old time fish houses lie. There are also fish markets on that side as well. It has been a while since I have eaten there, but Rose's Seafood stands out in my mind.
Another fun place is the Turtle Club, inside the bridge on the north shore of Clear Lake.
If you plan to hang out for a while, make sure you pick a restaurant on the channel. The Boardwalk has the best view. Once we were eating at the Dutchman I think when a go fast boat slowly cruised by with their speakers blaring rock music. One of the girls on it's deck jumped up and while shucking and jiving to the music turned around, dropped her thong bikini and mooned the shore based audience.
It still goes on there.
David