Tombow BC-AP54 Pressurized Permanent Ballpoint Pen (Can Write on Wet Paper/Back), Air Press to Squeeze Ink Ink, 0.7, Orange;

Affordable and clever little ball pen with robust plastic barrel and rubberised strips which are easy to grip in 'testing' conditions. The writing insert is pressurised when the mechanism is clicked meaning the Airpress can write underwater, upside down and even in non-gravity situations, perfect for outdoor pursuits, rock climbing or budding astronauts! Strong, spring loaded clip opens out very wide so it can be clipped onto straps, pockets and bags, small loop to attach a lanyard or similar for safekeeping.