You have two options:
1) McFaddin Beach is about 1.5 hours east and south of Houston. Take I-10 east to the town of Winnie, Texas. Exit there and take State Hwy 124 south through the town of High Island. About a mile past High Island, the highway makes a 90 degree turn to the right and heads toward Galveston via the Bolivar/Galveston Ferry. You'll see that the highway actually continues to your left as well but there are signs there that say "Road Closed." Just ignore these signs and drive past them. The roadway is fine for a mile or two before petering out into the sand (this is a section of Hwy 87 that used to parallel the coast but washed out in a hurricane back in the 80s and the state never rebuilt it, though sections remain intact here and there). Anyway, find a convenient place to transfer over to the hard-packed sand of the beach and drive well past the sign indicating that you've entered Chambers County and the one that follows shortly thereafter indicating that you've entered Jefferson County. After a mile or three, you should start noticing the nude people. Feel free to sprawl out naked as a jay bird here. One word of caution, this is not a legally sanctioned nude beach SO, always keep an eye towards both ends of the beach for sheriff's deputies. If caught, you could theoretically be arrested or ticketed but more often they just give out verbal warnings. Have a towel handy to cover up in case they do drive by and they'll leave you alone. One other thing, the farther along you go, the more likely you are to come upon gay sections. They won't bite so no reason to avoid them, but just be advised (I only mention it because you did). BTW, the water here isn't the cleanest (it's murky mainly from sediment washed into the sea from rivers but it isn't really very polluted) nor is the beach, but it IS the closest nude beach to Houston for certain.
2) Hippie Hollow in Austin. It's about 3 hours from Houston to Austin and about another 30 minutes west to Hippie Hollow. From Houston, take I-10 west to just past the town of Columbus. Turn right onto Hwy 71 west and follow it into Austin. About 1 or 2 miles past I-35 in Austin you'll see that the road forks. Hwy 71 continues on the left fork and the right fork becomes Hwy 360, also known as Capital of Texas Hwy. Take 360. Continue on 360 (it's a beautiful drive by the way) until you've crossed over the Pennybacker Bridge. It's a big wrought iron suspension bridge over Lake Austin and you can't miss it. Right after the bridge, take the first exit and turn left. This is RR 2222 (RR stands for Ranch Road). Take 2222 through the hills until you get to Hwy 620. Turn left on 620 and then take the first real road (not a driveway but an actual road) heading to the right. This is Comanche Trail. Follow the signs on Comanche Trail until you see the signs for Hippie Hollow. It's impossible to miss. Hippie Hollow is Texas' ONLY legal nude beach. I use the turn "beach" loosely because there's no ACTUAL beach (no sand anyway). There are, however, thousands of giant flat rocks to lie on. It's very beautiful. There are nature trails and the water is very clean and clear. Nudity is legal throughout (except in the parking lot). The cost per car, last time I was there (it was about a year ago I guess) was $10, but it could've gone up since then.