Damnoen Saduak is one of the well known and tourist friendly floating markets in Thailand. It's about 100 km southwest of Bangkok, or approximately 2 hours drive. Damnoen Saduak was actually the name of the canal dug in the rule of King Rama IV by the military men and people of Rajburi, Samutsakorn, and Samutsongkram Province. That time without canals, the river transportation was very slow.
Nowadays, Damnnoen Saduak is one of a provincial districts of Rajburi Province. Most people live along the canals, and majority of the people that live here are agriculturists. They grow a lot of different kinds of fruits and vegetables. The floating market is routinely crowded with hundreds of vendors and purchasers floating in their small row boats.
For the first timer to Bangkok, I would recommend to go here and it would be a great experience for you guys! It is best early morning before it gets really crowded and the heat of the day builds up. Make sure you bring your camera with you and take a lot of good pictures with these colorful scenes!