The Marais Potevin is just west of Niort and then it stretches across to the coast. This area is in Deux Sevres and La Vendee, but mostly in Deux Sevres and the tourist bit is the region close to Niort. Coulon is very popular and it has a pleasant quayside along the Sevre Niortaise which was once a major river taking shipping up to Niort.
There are several places where you can hire boats (embarcadere) either with a boatman or you can do the hard work yourself. You can go for one hour, one and a half, two or more, but the longer your trip the more it costs and if you are rowing yourself, the more exhausted you become.
On a recent visit (10th may 2012) we hired a boat from La Pigouille. They have their own Site de Pique-Nique along the prescribed route where you can stop and refresh yourself either by taking your own goodies or they will supply you with a hamper for a small charge. We chose not to pique-nique and instead took lunch at a restaurant called Quai Sud which is right next to La Pigouille as you can see from the photo. The food was excellent, helped by a lovely sunny day and a bottle of my favourite wine, Haut Poitou Sauvignon Blanc. A full review of this restaurant can be seen in the restaurant review page.
Apart from the peace and quiet of a boat trip and the mini workout it affords, there is also the wildlife which appeals to me. The Marais is home to lots of plants, birds and animals. We saw several rat-like creatures. I think they were coypu but they were quite quick to dive under the water and so could have been rats or even water voles. They were certainly not fully grown coypu as they are quite large. We heard golden orioles but did not see them as was the case with both green and great spotted woodpeckers. We did see a kingfisher but not a purple heron, though they are to be found there. The yellow flag irises were in flower as were the meadow buttercups making it all look very beautiful.