Can it be use to find the dive boat when you are underwater?
The H22PX would not be capable of locating your dive boat when you are underwater. You may get a distance reading if you were a few feet away likely you would not get a depth reading if you point the transducer towards the water surface.
If you need this to find the dive boat you have a problem of zero visibility. A great device to check depth,before you try to look at your depth gauge at the bottom. I have a habit of wondering how deep is that spot. Brought it to Hawaii ,but on a wreck at 80 feet ,75 ft visibility,what am I to point it at? In Cozumel at 130 wanted to point it all over to an endless depth,but have to safely keep with the group in fast moving currents. So a great item.If you need it to save your life, you have no common sense. Stan
i only used it on the surface to find depth to go diving.
Sorry to be unable to help you, but I only use the product to check water dephs.
Sorry , haven't tried to