I've always been suspicious of Damasko's use of martesitic steel for some of their cases. It is probably an alloy that is used for some stainless steel knife blades and, although it can be hardened, its carbon content would make it less corrosion resistant than austenitic steels such as 316L or 904L.
If the watch comes into contact with salt water it should be rinsed off and even sweat getting under the case back could cause pitting corrosion in the absence of oxygen.
For their dive watches, I see that Damasco uses an austenitic "submarine" steel.
PS:- A quick look at the English web site didn't reveal any serious errors, but perhaps I've become desensitised after nearly half a century in Germany. German advertising though does sometimes contain some pretty excruciating anglicisms. A commonly seen Dutch one (for beer) is "Socialise Responsibility". Wtf is that supposed to mean?
LOL ... I also have a Sinn U1 (Germanischer Lloyd rated 'submarine' steel) and so far the Damasko has fared no worse, ie. neither shows any sign whatsoever of wear or specifically rust/pitting.
PS. Here's a discussion of Damasko's steel and rust.