Many of the Mediterranean’s coastal waters around harbour cities like Marseille were polluted mercilessly in the past, and much of the local reef life died. Now there is change in the air: pollution has been reduced and artificial reefs encourage wildlife to return. Frederic will carry out wildlife population surveys here and oceanographer Sandrine Ruiton hopes that his results will be exceptionally accurate, since noiseless freediving is much less invasive than conventional diving methods.