WaterWriter allows you to write easily in wet, greasy or gritty conditions. It is pressurised so works when held at any angle, writes on all waterproof papers (and any other paper) without smudging and has a specially moulded outer to give excellent grip. Importantly, there is no spring mechanism in the pen, so grit/dirt cannot penetrate the inner workings. It really is the hardiest, most comfortable, pen out there. Put it in your pocket and it will not leak.
The triangular top minimises roll on table top whether in boats or planes.