When you have a huge body of water like the Thames it is the perfect opportunity for learning how to sail. Sailing is an all over body workout that is so full on that you forget you are even exercising! The Docklands Sailing and Watersports Club offers everything from private tutorial lessons to large group activities like dragon boat racing. It is fast, furious and open to elements, there is a really strong club atmosphere and the DSWC run many social events throughout the year (although it is also perfect for casual drop-in sessions too). If you want something a little more avant-garde then why not try learning how to windsurf?