Gonna make my response simple, so we don't all end up writing books.
ENW was dispersed
in the ocean. Nobody can disprove this fact. It is stated not to possess a brain or nerves, making it water with disembodied consciousness. Therefore, it couldn't be "knocked out" (which, even if it were, is still an ability for Saitama.)
This scan is almost definitive proof that the eyes control the water since the water that was a part of ENW was not conscious inside of Tatsumaki's TK ball. So there's no justification for the eyeballs being connected to the literal ocean, but ending up a small puddle.
After Garou
obliterated her, she
trickled off into the ocean and
very quickly became Evil Ocean Water. Before that, Atomic Samurai
also shredded her, and she reformed nearly instantly. Those scans also show her eyes can control water immediately around her without being inside of it, and
this scan shows her eyes are also liquid. Atomic Samurai confirms there is no central component that controls her or is critical to her existence. Comparatively, Saitama only parted her down the middle while she was
still in the ocean.
Drawing the line for suspension of disbelief here is odd, considering Saitama has resistance to immense cosmic radiation, can grab hyperspace portals, and can manipulate subatomic particles, all as abilities stemming from him doing a basic fitness routine for years.
ENW could have also not have the energy to reform after taking so much damage as it would essentially lose all the energy dispersed in its body after being disconnected from it
Diffusion doesn't require energy. Water doesn't take physical damage.