Poole Harbour is, by surface area, one of the largest natural harbours in the world. It is also, depending on the state of the tide, the time of year, the direction of the wind and the confidence of the person at the helm, either a sublime playground or a fairly efficient mechanism for making expensive mistakes. Whether you're arriving in Poole for the first time aboard a powerboat, planning a jetski session off Sandbanks or simply wondering why someone has positioned a whopp