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Websites | Books
Trimix diving
Beyond 50 metres, divers use mixed gas that has less nitrogen in it than the usual air mix. This is because nitrogen can have dangerous physiological effects if it is used at the high pressures that exist deep underwater.
Even at about 30 metres, breathing compressed nitrogen can cause a sort of euphoric, drunken state and confuse thought processes. The condition is called 'nitrogen narcosis'; more commonly known as being 'narked'. It takes people in different ways, one diver has even been known to pull out his air regulator and attempt to feed air to the fish!
There are two ways to deal with nitrogen narcosis. One is simply to ascend a few metres until the feeling goes, and the other is to avoid breathing so much nitrogen. Trimix is made up of oxygen, nitrogen and helium. Helium effectively replaces some of the nitrogen, which normally comprises around 71% of the air we breathe. Trimix is the most common choice of mixed gas for deep divers, allowing them to reach the 70-metre mark.
But Trimix diving is certainly not for everyone. Longer decompression times are necessary because the higher pressure at depth can lead to the bends. And the sheer complexity of Trimix means that it's very easy to make mistakes: different gas mixes for specific depths are required as well as different mixes for varying decompression periods – this means that careful planning and a clear head are essential for safety.
Drysuits have to be inflated to balance buoyancy and to provide some protection against underwater pressures. Air divers are able to do this with the same air that they breathe, but Trimix divers use argon because the helium in their breathing mixture cools the body. They have to carry an extra cylinder for this, which means that they may end up carrying three to six cylinders on any one dive (as opposed to one or two air cylinders).
Added to these considerations is the high cost of helium. All of which make Trimix diving a serious business.
Websites
Diving in Cornwall
www.cornwall-online.co.uk/waterside/diving.htm
Information about diving in the area.
The Haunted U-Boat
www.madladdesigns.co.uk/…
A fascinating account of the doomed UB65 whose crew members thought was haunted.
National Maritime Museum
www.nmm.ac.uk
Opened in 1937, the museum has the most important holdings in the world on the history of Britain at sea and the world's largest maritime historical reference library, including books dating back to the 15th century.
National Archives
www.nationalarchives.gov.uk/default.htm
National archive of the UK which brings together and preserves the records of central government and the courts of law, and makes them available to the public. The records span an unbroken period from the 11th century to the present day.
Sea Ghosts
www.nzghosts.co.nz/sea_ghosts.htm
Ghost stories and war stories including one about the German UB65 that sank in 1918.
Uboat.net
www.uboat.net
U-boat resource with lots of information, articles, forums, book reviews and much more for the enthusiast.
Wreck Diving
www.beyondmagazine.co.uk/…
Lists First World War U-boats sunk around the British coast between 1914 and 1918, including UB65.
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Books
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Battle Beneath the Waves: U-boats at war by Robert Stern (Cassell Military, 2002)
U-boats wreaked havoc on Allied merchant ships and their vital cargoes, but in turn suffered horrendous losses, vanquished by the superior tactics and dogged seamanship of their pursuers. Seventy percent of U-boat crewmen perished at sea. This is the story of the U-boat wars, from 1914 to 1945, recreated from the experiences of German survivors.
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Diver Guide: Dive south Cornwall by Richard Larn (Underwater World, 1996)
More than 200 coastal and offshore dive sites, including the area's infamous tally of wrecked ships, are described in a book that covers the area from Whitsand Bay to Land's End.
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The Submarine: A history by Thomas Parrish (Viking Books, 2004)
Tells the story of those who first dreamed of underwater ships; of the practical and ingenious inventors and engineers who created and developed the submarine.
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The Submarine Book: An illustrated history of the attack submarine by Chuck Lawliss (The Crowood Press, 2000)
Illustrated account of how the modern submarine fleets came to be, from the very first underwater vessel that crossed the Thames in 1620 to the ultra-computerised nuclear submarine that functions as the strategic linchpin for most of today's advanced navies.
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U-boat Hunters: Code breakers, divers and the defeat of the U-boats 1914-1918 by Robert M Grant (Naval Institute Press, 2004)
Looks at the role of the U-boat during the First World War and the fate of each, including UB65.
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Verschollen: U-boats lost during World War 1 by Dwight Messimer (Chatham Publishing, 2002)
New reference for researchers looking for accounts of lost submarines and readers who enjoy action and adventure stories. It examines in detail each of the 203 U-boats lost during the First World War.
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