There are three European species of Hydroglyphus, one of those can be found in Holland. That species, pusillus, is a common little beetle in new, "virginal" ponds. )¹

Both specimen on this page are from the same, newly dug pond with sand bottom where some of the other beetles of this gallery where found. Typical for this species are the two little grooves in the neck shield, that continue a short distance in the wing cases. And so the name part -glyphus, meaning grooved, is obvious. The color pattern is also typical, but rather variable as you can see on the darker specimen pictured below. The specific name pusillus means something like: tiny, dwarfish. Maybe the specific name is a relict from an older name: Dytiscus pusillus (Fabricius, 1781) - compared to other Dytiscus species this is indeed a dwarf.

)¹ De waterkevers van Nederland 1992 - uitgave KNNV