William T. Anderson discovered several coral reefs on the continental shelf. He claimed sole ownership and control over them. Atlantis (P) received whatever interest in the reefs that William Anderson had. Another group of corporations attempted to obtain a permit from the Army Corps of Engineers to develop the reef. P notified the United States of its claim to ownership of the reefs. The Government (D) brought an action against these other corporations for trespassing on government land and for erecting a structure on the outer continental shelf without a permit from the Secretary of the Army. P sought intervention, alleging that it had title to the property by discovery and occupation and that D had no territorial jurisdiction, dominion, or ownership over the reefs. P also filed a cross-claim against the other group of corporations for trespass. The district court denied the motion for intervention and P appealed.