During water searches the scent is carried to the surface as it travels according to water temperature, water depth, and air current. The search dog will alert when he finds the scent. Dogs usually work from a boat but can also work from shore. When working from a boat they usually work from the bow of the boat. The boat can travel back and forth from shore to shore. Keeping in mind the wind direction and other weather conditions such as sun reflection, temperature and currents of the water can affect the way the search is conducted. An alert from the search dog makes the handler aware and the rescue divers evaluate where to dive. It is just as important to know where not to dive. If you can determine where the victim isn't then you have valuable information, especially when you are searching a large area of water. In searching the water, the dogs can only detect where the scent is emerging from the water. The subsequent location and recovery of the victim is accomplished using other skills and equipment, such as sonar equipment, dragging tongs and underwater cameras. 

The most commonly used method to introduce the dog to human scent under the water is with a scuba diver. The process begins by introducing the dog to the water by swimming and riding in the boat comfortably. The diver can start with a run away from shore and moves to shallow water and is still visible to the dog. When the dog gives an alert, the diver rewards him.  After this systematic approach the dog and handler then precede to the boat, will search the area, until he can find the scent cone of the submerged diver. When the dog alerts, then the diver is given the signal to come up and will reward the dog. It is very important in training for the handler to know where the scent is in order to prevent a false alert. This is when the dog alerts in the absence of desired scent source. 

Any OVSAR handler participating in water searches must obtain water training in basic boatmanship and related water skills. Both the handler and dog must learn to be comfortable in small boats and be strong swimmers. The handler should know basic water reading skills. It helps to know as much as possible about the environment.