I have fished all over Galveston Bay System in a flatbottom boat like you are talking about. Over the last 25 years. When I was younger that is all I had. Fished Moses, Offats, Christmas and area, TCD, Trinity, East, West, and any where else it would take me. Just watch the weather and be careful. I even took it out to the Jetties and the Rigs 8 miles or so offshore on the right days. You talk about fun, Hang a Big King Mackeral or a 5ft. Black Tip in a boat like that and you don't need a motor. I run a 21ft. center console now and take it 40miles out on the right days. Had to tie it off to a rig and bail once or twice until the weather past on some overnight trips, but what an adventure. Get a map, Be Careful, Have fun and Good Luck. Start small. Its More about Knowledge, Confidence and what you are Comfortable with than anything else. Respect the Sea, but do not fear it.