Flooded Cave is the seventh stage in Squishy Cave.
If you don't have any anti-black characters, Beware the Shadow Boxer K and Gory Black, as they can push your lines far enough for the doge darks to hit your base.
Use long range cats such as Sexy Legs and Dragon Cat, along with Wall and Macho Cat to stall the blacks. Continue spawning the mentioned cats throughout the level. If you have any anti-black ubers, those can help too. Bomber Cat, a Freeze UP Combo, and something to defend Bomber Cat (like Wall Cat) can be very effective.
The name of the stage maybe is a reference to a cave full of water, as the name of the level states.