Salt is a mineral, so it's going to behave much like hunting over hot rocks. Most VLF-type detectors will have a hard time, but some older machines have a salt setting or have a wider ground balance adjustment to help compensate.
There's still a few things you can do in how you operate that may also help.
The salt/mineral effect is everywhere, but weak. A good target signal will be stronger. Raising the coil so you scan with it two or three or more inches above the sand will hopefully put the coil above the weak salt signal, yet still able to detect a shallow coin or ring. Lowering sensitivity will also help. Just try to find a point where the machine is not falsing but will still detect a test object buried a few inches deep. A smaller coil will "see" less of the salt and will be more effective than a large coil.
Expect target ID to shift due to the salt/mineral effect.
Hunt a narrow trail parallel to the water line so you are mostly within a certain sand moisture content. Heading up and down the beach, going towards and away from the water will present differing levels of moisture in every sweep. Also hunting parallel but using a wide sweep will tend to have varying moisture beneath the coil as it moves towards and away from the water. But keeping the coil in a narrow band of equal moisture and setting your machine to handle it will give more consistent results. Retune a bit each time you move to either drier or wetter sand. As you move away from the water, the effect should lessen and you can begin to lower the coil or increase sensitivity or alter ground balance.
-Ed