We report a case of transient neurological disorder compatible with cerebral decompression illness in a breath-hold diver. A large right-to-left shunt was later detected with contrast transcranial Doppler ultrasound. While the mechanism of brain damage is unclear, this observation highlights the need for breath-hold divers to avoid excessive nitrogen loading and to refrain from forceful Valsalva maneuvers that may contribute to the opening of a patent foramen ovale and lead to paradoxical cerebral embolism. Because decompression illness is a possibility, anyone who experiences unusual symptoms after breath-hold diving should seek immediate medical attention.