General Zaroff stocks his island by misdirecting passing ships using a simulated lighthouse. Rather than directing the ships to safety, the light leads the ships to the rocky shore. Those sailors able to swim to shore from the resulting shipwreck are captured and held prisoner until the General once again needs game to prey upon.
General Zaroff lives on an island known to sailors as Ship Trap Island. Sailors believe there is something mysterious about the island that captures the ships and crews and so the mood on the boat as they begin to sail passed it becomes very subdued and ominous. Like so many ships that sailed before them Rainsford's ship and crew fall victim to the "trap". It is not until Rainsford is inside General Zaroff's palatial estate that he learns the mystery behind the trap. General Zaroff shows Rainsford from a window that it is actually he who traps the ships. He then uses the sailors who wash up on shore as his "stock" for his most dangerous game.
"This island is called Ship-Trap," he answered. "Sometimes, an angry god of the high seas sends them to me. Sometimes, when Providence is not so kind, I help Providence a bit. Come to the window with me. . ." Rainsford saw a flash of light. The general chuckled. "They indicate a channel where there's none, giant rocks with razor edges crouch like a sea monster with wide open jaws. . ."
When General Zaroff turns on the lights for his fake channel to trap ships, he deliberately makes the approach deadly because he misdirects the ships to "giant rocks with razor edges [that] crouch like a sea monster with wide-open jaws." The lights indicate a channel "where there is none," he says to Rainsford. When the ships wreck, the survivors of the wreck become Zaroff's prisoners and therefore his "game."