There are there main environments that all require different things from a metal detector and that is whether they are on land, in saltwater or in freshwater. If you were predisposed to the ownership of all the money in the world, then you would maybe want to buy three metal detectors for each scenario, but most people do not have that kind of luxury to be able to afford to do such things.
So, if you want a metal detector that can do all three things, then you need to take into consideration what type of model you would want. Pulse induction detectors work better in saltwater, so, if you are looking for a model for both types, then it is probably best that you go with that one.
If you are looking for an underwater model that you can use out of the water, then you will also have to think about the weight as underwater models need to have that added weight to them to counteract the buoyancy of the water, and this means that they might be very heavy when they are on land. It is vital that you check the weight to make sure that it is something that you will be able to handle.
Extra accessories are usually a nice added feature to have when you are buying any product and that includes metal detectors. Some of them usually come with just the device while others will throw in some extra items.
One of the biggest ones, if your detector requires them, is headphones, as these will let you know through deeps about how close you are to finding something that is important. It is equally important to know that a lot of these models do not require headphones at all and instead they rely on vibrations and LED lights.