The wetlands at Getterön were created in the 1930s, when the shallow strait between the mainland and Getterön was filled out.
Why the captain guided the Antilles into the narrow shallow strait is still not known.
The Orchid could slip through far shallower straits than that.
A few islets are situated in the 1-1.5 km wide and shallow (2-4 m deep) strait between the two islands.
The most powerful whirlpools are created in narrow, shallow straits with fast flowing water.
At the western coast of the island of Amager a large area was embanked from the shallow strait of Kalveboderne in the 1930s.
It is especially noted for two islands in its center, separated by a narrow, shallow strait (both of which have cabins).
This suggests that there was a shallow strait as narrow as 20 km, which may have frozen completely at times.
The Baltic Sea is connected to the ocean through the narrow and shallow Danish straits and belts.
These pose a collision hazard in the narrow and shallow strait.