The correct answer is D) directly under the boom. When personnel are being lifted from a vessel in a personnel basket, the vessel should be positioned directly under the boom. This ensures that the personnel basket can be lowered safely and securely onto the vessel, minimizing the risk of the basket swinging or colliding with the vessel. The vessel should not be stopped dead in the water (option A), as this could make it difficult to maintain position under the boom. It should also not be moving away from the boom (option B), as this would create a dangerous situation. Tying the vessel to the boom (option C) is also not recommended, as this could restrict the vessel's movement and increase the risk of the personnel basket hitting the vessel.