I'm not sure of a good marina to launch your boat, but there serveral places to visit in the Clear Lake/Galveston are. One of the best anchorages on the Texas coast is Offats Bayou in Galveston. If you can, find a copy of "Cambell's Guide to Cruising Texas", there is a lot good info about marinas and anchorages all along the Texas Coast. There is also Campbell's Guide website,
The Walter Eden Company, Inc.
Good Luck,
Rodger