In my opinion, the wet sand is the real proving ground for metal detectors or search coils intended for beach hunting, you can add waterproof pin-pointers to that list too.
Salt levels change daily at beaches and black sand can show up after beach erosion or rough surf churns up the lower beach.
Tweaking a VLF metal detector sensitivity or PI metal detector gain to suit the beach conditions is important, the reason I never turn my sensitivity control or gain to a certain level and forget it.
I see that advice passed around on metal detecting forums, set your metal detector sensitivity to a certain position and off you go.
That is ok as long as you are going to check and adjust the sensitivity level at some point to suit the ground you are covering.
At saltwater beaches you need to adjust the sensitivity on your VLF metal detector to suit the salt levels present at the time you start metal detecting.
Not the same sensitivity level you used last time at the beach or the level you use all the time at the beach.
The whole point of having a sensitivity control is to be able to adjust it so your metal detector is running smoothly and detecting a wide variety of targets at various depths.
Depending on the beach, you may be able to run hotter or it may be better to back off the sensitivity.
My advice is to find a starting point, start searching and then tweak the sensitivity.
Increase it to a level that causes a little chatter then back it down to where it runs smoothly.
If you are running noisy at the level you first chose, back off the sensitivity.
Find the slightly chattery level and then the best or most comfortable operating level.
Too much chatter or too many false signals will cause you to miss good targets.
Lowering your threshold volume a little usually helps to smooth out and compliment a well adjusted sensitivity level.
Don't be afraid to use Auto sensitivity if you have it and it allows you to run smoother.
Sometimes it is better to detect all targets instead of missing targets because you are running too hot.
Just because you are using a VLF metal detector it does not guarantee you have an advantage using discrimination, if you are losing depth or missing shallow targets because of sensitivity setting issues.
Get in the habit of adjusting your metal detector sensitivity control to suit the conditions you are about to search.
Remember just like driving a car, low dipped highlights in the fog are better than using full beams. Saltwater beach example, a lowered sensitivity level will help you to see through black sand and detect targets.
High car beams in open areas, allow you to see greater distance ahead.
Beach example, a higher sensitivity level will help you to cut through the sand and detect deeper targets.
Your metal detector sensitivity control should never be a set and forget control unless you run in Auto, as conditions always change.
Set your sensitivity to suit the real time conditions at beaches as they change from day to day and sometimes from one tide to another tide.
Are you setting and forgetting your sensitivity control, or are you maximizing your metal detectors sensitivity to detect small shallow targets and detect large targets at depth?
In other words, are you leaving stuff behind for the next beach hunter because you do not take advantage of one of your metal detectors best assets.