Akwai mashigar ruwa mai matukar muhimmanci a Denmark, tunda ta raba yankin Jutland Peninsula da Sweden ban da shiga Tekun Baltic da Tekun Arewa. An suna Kattegat Ruwa kuma yana da tsayin kilomita 220. Akwai tsibirai da yawa da za a iya gani tare da mashigar ruwa, kodayake Samso, Laeso da Anholt sun fi girma.
Sunan mashigar ya fito ne daga kalmomin Dutch biyu. Daya shine "kat" wanda ke nufin kyanwa, yayin da dayan kuma "gat" wanda ke fassara zuwa rami. Don fahimtar dalilin da yasa wannan nadin dole ne mu koma zamanin Zamani. An ce a wancan lokacin yana da matukar wahala kwarara ta cikin ruwansa, saboda kasancewar kunkuntar (ta yadda wani lokaci ana daukarta azaman bay) samuwar sandbanks ya zama ruwan dare gama gari.
Kamar yadda muka riga muka fada, Kattegat ya cika muhimmin aiki, tunda raba kasa biyu, waɗanda sune Denmark da Sweden. “Ungiyar "International Hydrographic Organisation" (IHO), wacce ita ce kwayar halitta tare da babbar hukumar ƙasa da ƙasa idan aka zo batun kafa iyakar teku, tana ɗaukar wannan mashigar kamar ɗaya daga cikin tekun ta kuma ba ta lambar 2 a matsayin alama.