I think it is really super that the Port of Houston Authority gives free tours. In a day and age when hardly ANYTHING is free anymore, this is a refreshing service they offer! They even offer you a coke or coffee on the trip – free of charge. You can sit inside and look out the windows, or stand outside and feel the wind blowing by (to see a picture of the actual coast guard boat you ride in, click the Port of Houston Authority link above).
There are restroom facilities at the port’s Sam Houston Pavilion where you board the boat, and there are restrooms on the boat itself. Each tour is limited to a maximum capacity of 100 passengers, but we have never had any trouble getting a seat on the days we have gone. We have taken this tour twice now, and enjoyed it both times.
For a free field trip, the Houston Ship Channel is top notch!
Another Review with helpful tips can be found here: Frommer’s Review by David Baird