Sweden's territorial sea and internal waters have experienced regular intrusions by submerged foreign submarines since the early 1950s. The response of the country to such intrusions is generally well-documented and mainly public. The present article offers an overview of the development of the relevant national legislation, the actual response of the naval forces, and the legal arguments invoked at national level to justify or dismiss use of force in self-defence or under another title. The article discusses the relevance of the immunity that submarines normally enjoy under international law and Sweden's human-rights obligations, two issues that have been at the centre of the legal discourse. Particular attention is paid to developments since 2014 when a new round of "submarine hunts" started and led to the adoption of new measures both revising the existing laws and strengthening the defence forces.