Final answer:
In a crossing situation, the give-way vessel must not cross ahead of the stand-on vessel as this might lead to a collision according to the International Regulations for Preventing Collisions at Sea (COLREGs).
Step-by-step explanation:
If you are aboard the give-way vessel in a crossing situation, what you should NOT do in obeying the Rules is to cross ahead of the stand-on vessel. The actions that a give-way vessel is recommended to take include making a large course change, which should optimally be to starboard to avoid confusion and in accordance with maritime navigation rules. Slowing down or stopping your vessel is also a potential maneuver to avoid collision.
However, crossing ahead of the stand-on vessel could result in a close-quarter situation or collision, especially if the stand-on vessel is unable to maneuver in time or if distance and speed judgment under stress is miscalculated. This action is not advisably taken as it directly contradicts the international navigational rule commonly referred to as the International Regulations for Preventing Collisions at Sea (COLREGs), specifically Rule 15, which dictates that the give-way vessel should avoid crossing ahead of the stand-on vessel.