The Grand Aquarium de Saint-Malo is one of the major aquariums in France, located in the modern part of the city about 4km from the Intra-Muros. It is best reached by the tourist train that runs from the old city, or by car. The exhibits cover Atlantic species — including a good shark tank — alongside tropical fish from around the world and a deepwater display that recreates the experience of an underwater submersible descent.
It is excellent for children and more scientifically serious than many tourist aquariums. The nautical heritage section, which covers the history of deep-sea exploration by French oceanographers, is particularly good. Allow two to three hours. Entry is moderately expensive by French standards, but the combination ticket with the castle museum offers a saving.