When the paramedics arrived at the house at the beginning of the episode, the male paramedic says he was still out of breath from giving mouth-to-mouth at the previous call. However, paramedics would never administered CPR via mouth-to-mouth; rather, they would use a bag valve mask (BVM), or what is more commonly known as an "ambu bag."
When Brody and LaSalle discover the car is in the river, there is no way the GPS of the vehicle could still have been working, let alone able to get a radio signal out underwater. The entire electrical system of the car would have been fried from being submerged thus disabling the GPS transmitter.