Alright, I have a semi-good suggestion to make this card more realistic.
Flooding doesn't occur in rows, it occurs across a large area. Killing creatures would make it way too overpowered and unrealistic, unless it's flood is made of acid. So, here is my suggestion:
Flooding happens for 5
![Water :water](https://elementscommunity.org/forum/Smileys/solosmileys/../../../images/Misc/water18x18.png)
per turn. When played, the ENTIRE field is flooded, and all creatures that are not airborne / water / neutral will be in a time bubble for 3 turns, and after the three turns they die (suffocate).
Specific digits can be changed, of course, but you get my drift.
Flood = unable to attack, slowly dying
Flood != immediately die in certain areas