What can I do to stop the water from accumulating ion the car?

Yes water test it with a hose while someone is in side the car looking for leaks.Water test the hood fender windshield under hood etc.There is no magic answer for a water leak i have had to fix and too many to count.

THERE'S PROBABLY A DRAIN FOR THE A/C ON THE FIREWALL (ENGINE COMPARTMENT) IF IT IS STOPPED UP, THE WATER WILL USUALLY OVERFLOW INSIDE.....SOMEWHERE

NOT ONLY DOES THE A/C MODE PRODUCE CONDENSATION, THE DEFROST MODE IN THE HEAT MODE DOES IT ALSO, AS IT SORTA "DRIES" THE AIR PRIOR TO IT BLOWING AGAINST YOUR WINDSHIELD.

HERE'S MY LAST POSSIBILITY....SEE THIS LINK

https://www.2carpros.com/questions/2005-ford-mustang-water-leak

LET US KNOW HOW IT GOES

THE MEDIC

Thanks medic had a mind fart there was thinking a water leak from rain didnt think about the ac drain.Look at the firewall behind the engine about half way down in the middle you will see a hose a or hole.That would be your ac drain if its a hose try milking it to see if water comes out.If its a hole use a metal coat hanger see if the drain leaks water.Also not all cars run the ac in defrost mode yours may or may not but not all cars do.

I would say it is a water leak rather than the A/C drain hose which is on the passenger side.

Depending on the weakest part of the ac box water tight wise is where it will like from when filled with water.Check the drain if its good back to my oringal answer.