The purpose of this paper was Io study the water chemism in hydrokinetic arrangement Elbląg Bay - Elbląg River - Lake Druzno, which may be qualified as quasiestuary arrangement because of only periodical penetration of salty waters upwards of it. The measurements showed, that in about 20% of taken samples these was evidence of water intrusion from the Vistula Bay to estuary. It was found out that inlets were either into the whole estuary, so-called complete intrusion, or only into the part of it, in such case, salty waters reached only the northern part of Lake Druzno, so-called incomplete intrusion. The registered inlets occurred only in favorable hydrometeorological conditions. The kind of intrusion, complete or incomplete, was depended of hydrometeorological situation