D is a government contractor operating on the island of Guam. D maintained a recreation center near the shoreline for its employees. The shoreline had a channel so dangerous for swimmers that its use was forbidden and signs to that effect erected. John Valak, the employee, spent the afternoon at the center when he saw or heard two men, standing on the reefs beyond the channel, signaling for help. A large group of people went to help. In attempting to swim the channel to reach the two men he was drowned. A claim was filed by his mother. P found as a 'fact' that 'at the time of his drowning and death the deceased was using the recreational facilities sponsored and made available by the employer for the use of its employees and such participation by the deceased was an incident of his employment, and that his drowning and death arose out of and in the course of said employment . . . .' P awarded a death benefit of $ 9.38 per week. Ds petitioned the District Court under § 21 of the Act to set aside the award. That court denied the petition on the ground that 'there is substantial evidence . . . to sustain the compensation order.' The court of appeals reversed. It held that the lethal currents were not a part of the recreational facilities supplied by the employer and the swimming in them for the rescue of the unknown man was not recreation. The Supreme Court granted certiorari.