What automatically deploys when the raft is inflated?

When a life raft is inflated, it typically deploys a sea anchor. The sea anchor, also known as a drogue, is designed to keep the raft positioned and stabilized in the water, especially in rough conditions. This is crucial for preventing the raft from drifting away and helps maintain its orientation relative to waves and currents, ensuring the safety of the individuals onboard.

The other options do have their purposes in maritime safety and emergency situations. A buoy may provide additional visibility or flotation but is not a standard feature that deploys automatically with the raft. A whistle is a signaling device that users may carry but does not automatically deploy with the raft. A radio beacon is also an important safety device for sending distress signals, but it is not automatically included in the initial deployment of a life raft. Therefore, the sea anchor stands as the correct answer due to its direct role in enhancing the effectiveness and safety of the raft once it is deployed.