12v battery dead and then dead again

Last weekend, during overnight of Saturday April 21st, we got a hard rain and our street flooded. Water got into the floor boards of our 2005 Prius. I noticed this on Monday when I went to drive the car to work. The battery was dead and had to jump the car to move it to our carport to let it air out for the day (I jumped it with jumper cables from another vehicle to the 12v terminal connections on the actual battery). I let it sit all week with a dead battery and airing out the car. Windows down and doors open.
The weekend after, April 28, we got a new battery (it was under warranty because we purchased it in January of this year), I put it in Saturday morning. The car car came on when connecting the batter, I turned the car off. I pushed the start button again and it came on and said the key was missing (which I didn't have at the time), so I turned the car off again. I closed the doors and left the windows open. I couldn't find the key until Monday.
On Monday evening, April 30, I tried unlocking the car with the key fob and no luck, although the light on the fob works. I jumped the car again with the new battery (this time with a portable jump starter and used the connections in the engine) and drove it to the gas station to fill it up. I jumped it to get back home. When at home, parked, tried to roll up the back windows and the car died.
Haven't messed with it since then.
I drive it 4 days a week, 35 miles each day. It has 120,000 +/- miles on it, I'm on my 2nd hybrid battery (which had more than half charge when I was driving it to the gas station).
Any ideas on what is draining my 12v battery like this? IDK why the battery was dead when water got in the car to begin with. IDK why the new battery died so fast.