William, a thirty-year-old man, lives alone in a caravan in the middle of nowhere. A former competitive swimmer, he spends his days diving without a tank in a swimming pool a few meters away from his caravan. With each dive, William gets lost in his dreams, which change depending on his mood and his everyday life. Deemed a depressive, he is being treated by Sonia, a strict and unsympathetic home care nurse. One day, Sonia leaves on vacation and is replaced by Lucie.