Reverse osmosis for desalination?
Reverse Osmosis will desalinate water.
If you apply a RO system expecting well water or municipal water to raw seawater desalination, you will very likely experience short membrane life .vs. a system optimized for that job, which might have many more pre-filters, for one thing.
Likewise, as far as I recall from not very recent research, RO membranes intended for use with well water are different from those intended for use with municipal water (in the context of the vast majority of United States municipal water being chlorinated, and well water usually not being chlorinated.)