Nissan Repair: Noise while driving., nissan altima, soothing waves

Question
This is a strange one.. I have an '02 Nissan Altima and I hear water/liquid 'sloshing' around while driving. My first reaction was to look in the back seat to see if my husband had gallons of water back there. It's not very loud, it sounds a bit like soothing waves. I don't know if it's necessary to mention that I just picked up the car from having the dash repaired-- I don't think that has anything to do with the sound I'm hearing, but it's a weird coincidence that I noticed it the same day I picked up the car. Any idea what it could be?

Answer
Alison,

It could be the airconditioner box, under the dash, that has a blocked drain.  I would check that first.  Also, look under the seats as I have found that people tend to leave things in the car.  There could be a bottle of water under the seat.