1 – Pulicat Lake

This is a very large water body at the border of Tamil Nadu and Andhra. Its off NH-5 (highway from Chennai-Nellore-Kolkota). We visited there once and it was a beautiful experience. The highway is very well laid and you can travel in speeds of 90-100Km/hr easily. There are very good scenic views on the journey (like good greenery, paddy fields etc). We reached a fishing village which lived on the banks of this huge lake. People there were simple and friendly. We paid about Rs.100 to a fisher man and he took us around the lake (ofcourse we did not cover the whole lake, its huge).

People in chennai – this is a good place to visit – definitely a change from the usual Spencers, Besant Nagar etc.

For more information see the Wiki link:
http://en.wikipedia.org/wiki/Pulicat_Lake

2 – Muttukadu

This is a scenic stretch of backwaters on the road from Chennai to Pondicherry (on the East Coast Road) about 90Kms from Chennai. The drive is very pleasant as they ECR (East Coast Road) is very smooth.

There are boating rides available – speed boats and usual motor boats. We tried the speed boat and it was excellent. Its a little costly (I guess around Rs.250). Its a short ride, but they do all kinds of tricks with the boat and you will enjoy the ride. They asked us if we wanted to go to the sea for an additional Rs.100, we didnt opt for that. Its a decent place to relax around Chennai.

The below link from Hindu had more details:
http://www.hindu.com/mp/2004/07/24/stories/2004072400240100.htm
(dont know when this link will expire)