Wet, but no nails
There are plenty of workplaces where the floor is wet but nothing sharp is lying around: a scullery, a dairy company, a cleaning crew or a care home. That's exactly what S2 is for. The upper is tested for water penetration, the construction is anti-static and the heel absorbs shocks, but the penetration-resistant sole of S3 is missing, which saves weight and flexibility.
Water-repellent is not waterproof
S2 means the leather or textile barely lets water through during a test period. If you stand in water for hours, the shoe will still fill up and you'll need an S4 or S5 boot. Regular cleaning and waterproofing keep the water-repellent effect intact for much longer.