We have traveled to Cannes annually since 2000, and Coquillages Brun is a "must do." It's not about the setting - the restaurant itself is "no frills" - it's about the seafood. You won't care about the lack of decor.
The restaurant is on the corner of Rue Felix Faure and Rue Louis Blanc, and before it's brought into the kitchen, the seafood is prepared outside the restaurant along the Louis Blanc sidewalk. It's that fresh. There are plated menu selections, but the best is to order a variety of seafood that will be brought to you on a tiered stand. Everyone at your table picks off of those plates and it's wonderful. My favorite was actually the perriwinkles that were brought to us as an appetizer that I don't think we ordered and may have been complimentary. However they ended up on our table, they made me happy and writing about them makes me wish I was there. The scampi were wonderfully tastey and my husband got his ever favorite oysters. Whatever you order, you won't go wrong dining at Coquillages Brun. Service was prompt and efficient. People wait to get into this restaurant, so they don't waste time getting the food onto your table.
if you don't want to wait, go early to Coquillages Brun. My husband attends a convention that generates a lot restaurant traffic, and I think the conditions during this meeting would be similar to peak season tourism. We arrived at the restaurant early (around 19:00) and were able to be seated without waiting. The restaurant filled up quickly and by the time we left, there was a crowd outside that restaurant waiting to be seated... and I mean a crowd that wasn't easy to walk through. Neighboring restaurants had many empty tables, and that's how good Coquillages Brun is. People don't mind waiting, and we'll be going back (but early!).