Final answer:
The event that is LEAST likely to happen next is that Gres will continue swimming smoothly and confidently. The most likely event to happen next would be Gres to make a final push and try to overtake the boy ahead of him to win the race.
Step-by-step explanation:
The event that is LEAST likely to happen next is that Gres will continue swimming smoothly and confidently. The passage provides details about Gres' current situation and mentions that there is only one boy ahead of him. This suggests that Gres has reached the final part of the race.
Therefore, the event that is LEAST likely to happen next is that Gres will continue swimming smoothly and confidently because he is already nearing the end of the race. The most likely event to happen next would be Gres to make a final push and try to overtake the boy ahead of him to win the race.