What should be done as soon as a boat is waterborne after being launched from the side of the ship?

After a boat is waterborne following a launch from the side of a ship, one of the immediate tasks is to release the aft hook. This action is crucial because the boat is typically secured to the ship with lines or hooks to prevent it from drifting away during the launch process. Releasing the aft hook allows the boat to freely maneuver in the water and ensures that it can operate safely without being tethered to the ship, thereby preparing it for its intended mission or activities.

In the context of boat operations, securing the bow line comes into play later, once the boat has been stabilized in its operational position. Checking fuel levels and raising the engine are also important steps, but they typically occur once the boat is confirmed to be safely operational and prepared for use. Thus, releasing the aft hook is the most immediate and necessary action to take to ensure the boat is ready for navigation and not restricted by any lingering connections to the mother ship.