Final answer:
The vessel that must take early and substantial action to avoid a collision in a crossing situation is known as the Give-way vessel.
Step-by-step explanation:
When two vessels are in a crossing situation on the water, the vessel (vessel A) that must take early and substantial action to avoid a collision is called the Give-way vessel. According to the International Regulations for Preventing Collisions at Sea (COLREGs), the Give-way vessel is obligated to take action by altering its course or speed to safely pass behind the Stand-on vessel, which has the right-of-way.
The Stand-on vessel should maintain its course and speed unless it becomes clear that the Give-way vessel is not taking appropriate action. In a crossing situation on the water, when two vessels are approaching each other, the vessel that must take early and substantial action to avoid a collision is called the give-way vessel.