This is the HK GP11 the underwater pistol. At least this is the first commercially pertussis
Produced variant.
>https://en.m.wikipedia.org/wiki/Heckler_%26_Koch_P11

You may say that despite having a pepper box layout these would have no other similarity. Sort of true, sort of missing the point.

It's an special purpose weapon which sort it fills the same role, and when you realise how many applications the p11 SPW has you will realise how many similarities there actually are.