Garrett has been making an aftermarket chip for tough and/or high salt/high iron ground for the last 2-3 years for the 1250, 1350, 1500, and 2500 series. The standard models don't work worth a hoot in soil like mine (as a matter of fact, they suck) and in the rest of the iron belt of N America too, plus other soils, so Garrett not only installed the chips on some of the newer models, they also made the aftermarket chip for some of the older ones. I have seen only 2 or 3 Garrett users in my area for many, many years and it's because other detectors usually handle the soil a lot better.
I beleive that if you contact Garrett and send it to them that they can install an aftermarket chip for you. If not, perhaps Keith Wills at: East Texas metal Detectors can do it for you, or perhaps modify it himself. Keith is often backed up with his work because of so much of a demand for his fine detector modifications and repairs, but he is very knowledgeable.
Or, you could so as Sandman suggested, trade it off for a Minelab because they are the smoothest running detector anywhere for beach hunting.