There is a nice one near the harbour.

Here is the url http://www.hotel-sete.com/

I would suggest you the Hotel Venezia, charmant and fairly prices, nice view, close to the Corniche, really 50 meters from the beach and to to go to the center of Sete, you have to walk only 20 minutes along the Crniche. I've been there 10 years ago, I think it should be better than it was, and it was great!

Try any of the Hotels along the Corniche. There is one right at the beginning called The Marina. And there's several located around Place Edouard Heriot. These in particular are good because of the them being situated between the sandbeaches and the old town.