This 2012 video says about itself:
A narwhal‘s tusk makes it weird among whales. It’s actually a tooth that can reach 10 feet in length, and scientists have numerous theories about its powers and purpose.
From the Royal Belgian Institute of Natural Sciences:
Narwhal in the River Scheldt Probably Died of Starvation
by Sigrid Maebe
On 27 April 2016, a dead narwhal was found in the river Scheldt, near the sluice of Wintam (Bornem). The autopsy revealed that the animal probably died of starvation. The narwhal is an arctic species that has never before been observed in Belgium.
An autopsy was carried out on the stranded narwhal in a joint effort by scientists of the Royal Belgian Institute of Natural Sciences (RBINS), the University of Ghent and the University of Liège.
The advanced state of decomposition makes establishing a cause of death difficult. However, no traces of a ship collision were present. The emaciated condition and the out of range position (more than 100 km away from the sea, and many thousands of km from its home range), indicates a natural process of starvation. Narwhal normally eat fish, crustaceans and cephalopods.
No food remains were found in its stomach or intestine, but, in the stomach, a number of small plastic items and small pieces of eroded driftwood were found. These items are very common in the river Scheldt and are concentrated in certain areas. Their presence in the stomach of the narwhal would indicate that the dying animal had swallowed them in the river and not at sea. We speculate therefore that it had swum up the river, and had died there shortly afterwards. The autopsy also revealed a heart condition and possibly also a thyroid problem. Several examinations and tests have started, including genetic and parasite analyses.
The stranded narwhal was a juvenile male with a (body) length 3,04 m long and a girth of 1,81 m. The tusk protruded 0,7 m out of its body (it can be 3 m long in adult males). The narwhal weighed 290 kg which is more than 150 kg too light for an animal of this length.
This is the first record of a narwhal in Belgium. Only a handful of observations and strandings are known in Europe, including an animal that was killed in the (former) Zuiderzee (The Netherlands) in 1912. Narwhals usually stay north of the 70° North latitude, and their home range includes arctic waters of Russia, Greenland and Canada. This is probably the most southerly record from Europe.
The skeleton of the narwhal will be prepared, and will be taken up in the collection of RBINS. RBINS would like to thank all persons involved in the discovery, securing, transportation and study of this exceptional animal that was discovered in a very unusual location.