Final answer:
The boat required to maintain course and speed when a risk of collision exists is known as the 'stand-on vessel'. It is generally the boat that is on the starboard side of the other in a crossing situation, as outlined in the 'International Regulations for Preventing Collisions at Sea' (COLREGs).
Step-by-step explanation:
When a risk of collision exists at sea, the rules that govern which vessel should maintain course and speed are described in the 'International Regulations for Preventing Collisions at Sea' (COLREGs). Specifically, the boat that should maintain its course and speed is referred to as the stand-on vessel. In a crossing situation, the stand-on vessel is usually the one to the starboard side of the other (on the right side when looking forward).
According to Rule 17 of the COLREGs, the stand-on vessel must maintain course and speed, whereas the give-way vessel has the responsibility to take action to avoid a collision. This typically means altering its course, reducing speed, or stopping. However, if it becomes apparent that the give-way vessel is not taking adequate measures to avoid a collision, the stand-on vessel must be prepared to take evasive action at the last moment to ensure the safety of both vessels.
All mariners must be familiar with these rules and ready to apply them when navigating waters where other vessels are present. While the ultimate goal is to avoid a collision altogether, understanding the responsibilities of each vessel when a risk is detected is key to maritime safety.