After WW2 the area was used as a dumping ground for explosives and considered dangerous. It has been suggested that and area between Bigbury Bay and Prawle Point in Devon, UK. may affect the ships compass because of the iron that has been regularly mined in the area. The Spanish and the Portuguese during the 15th century considered 1 degree to be 70 miles of 5,000ft each, or, 17.5 leagues of 4 miles. The English and the French worked 60 nautical miles or 20 leagues of 3 miles. The Dutch worked 60 nautical miles or 15 leagues of 4 miles.
Bronze disintegrates very slowly in sea water.
2,000 years in normal circumstances would have caused little damage. Barracuda seem attracted to glistening or sparkling objects. The three largest barrier reefs are off Australia, Florida Keys and Belize.