Appeared in DIVER December 2009
When nitrox is free, all well and good, but when you have to pay for each fill, you want to make the most of it. John Liddiard offers some tricks you may not learn on an advanced nitrox course. So what is a Scapa Fill?
Most Scapa Flow dive-boats are equipped for on-board nitrox
dive-planning time in Stromness, home of the Scapa Fill
getting the benefit