I did my undergrad in College Station and got my masters at A&M Galveston. From what I could grasp from the undergrads I knew, the Galveston campus was more like Aggie Lite. They tried to keep the traditions and such, but it wasn't as big a part of student life. It is a very small campus and it does have a history of being a "back door" into the College Station campus. Supposedly, if you didn't have the grades to get into main campus, you could say you wanted to be in the Marine Biology program and get into Galveston, then transfer to College Station after a year or two. This doesn't make sense to me because the Galveston campus is not a separate entity from College Station, but it's just what 'they' say.
As for academics, many of the profs at Galveston have taught in College Station at some time or another. You degree will say TAMU, not TAMUG, so don't worry about not getting full Aggie credit for you diploma. The campus is not on Galveston island, but on a dredge spoil island (Pelican) across the Galveston channel. This helps to keep the ghetto away from campus. Hope this info helps a little and is what you were looking for. There are some really good people involved with TAMUG and if you're interested in the marine environment or industry, I would recommend it.