The sailors who were captured into the bubble were naturally facing an indescribable situation.
Those captured sailors couldn't stay in the bubble for long, so there was originally nothing but a barren land inside the bubble, which is why the merfolk were so reckless in filling it with water, simply to prevent others from digging tunnels to escape.
Under normal circumstances, the sailors sent into the bubble couldn't last long, so the merfolk wouldn't provide the trapped sailors with food.
When those in the bubble saw an opening above, they naturally assumed a leak might have occurred and wondered if they could escape through this breach. So they all gathered around it.
As they approached and saw the opening in the bubble, although a few merfolk were near the breach, they didn't pay them any mind.
