NERO ALMOST died.
If William didn't pull him out of the water, he would have drowned. He was in his spirit form so he didn't think it'd be possible until he couldn't breathe underwater. This was already his 5th time jumping in the water and he still couldn't dive deeper.
"I told you it wouldn't be easy," William said, then he squatted down beside him. Then, he touched his shoulder. As soon as the Grand Spirit did that, he felt warmth spread all over his body until he was dry. Yes, the "water Mana" works like real water. Thus, he was soaked when he got out of the water earlier. "Did you see anything this time, Nero?"
Nero took a deep breath, then he nodded before speaking. "A water snake with red eyes," he said. "A large one, It slapped me with its tail as soon as it saw me. That's the reason why I lost consciousness earlier."
Thus, he almost drowned.