Yes, yes, and maybe. The island in question is Hans Island and is disputed territory between Canada and Denmark due to some historical quirks,
According to World Atlas, Hans Island is located in the middle of the 22-mile wide Nares Strait, which separates Greenland, an autonomous territory of Denmark, from Canada. Due to international law, all countries have the right to claim territory within 12 miles of their shore.
As such, Hans Island is technically located in both Danish and Canadian waters. World Atlas notes that the island was decided to be Danish territory by the Permanent Court of International Justice of the League of Nations in 1933.
However, as the League of Nations fell apart in the 1930s and was then replaced by the United Nations, the ruling on the status of Hans Island carries little to no weight.
It is true that the militarizesmilitaries of the respective claimants visit the island and both leave their national flag and schnapps or whiskey it is unclear if these are meant as gifts or as a a territorial makermarkers.
In 1984, Canadian troops made a fateful voyage to Hans Island. In addition to planting Canada's flag in the rock, they also left behind a bottle of Canadian whisky. Just one week later, a Danish official visited the island, replacing Canada's flag with Denmark's and replacing the whisky with a bottle of Danish brandy. He also upped the ante a bit, leaving a note that wryly welcomed visitors to Denmark.
"[W]hen Danish military go there, they leave a bottle of schnapps," Danish diplomat Peter Taksøe-Jensen tells WorldAtlas. "And when Canadian military forces come there, they leave a bottle of Canadian Club and a sign saying 'Welcome to Canada.'"