On the coast we race over a standard 2km distance. However we do so with a difference, starting and finishing in the same place and racing from the start line out for 1km to a buoy, executing a 180 degree turn and then racing back again. This is done for many reasons among which are, spectator viewing, the lack of 2km stretches of straight uninterrupted coastline and so that boats can be turned around quickly for use by others crews.
The buoy turn is a vital part of each coastal race, getting it right or wrong can mean the difference between winning and losing. Having a buoy turn in the middle of the race is also the reason why coastal boats are rigged the other way around to standard rigging on river boats. The turn must be taken clockwise and hence it is quicker to get round with the stroke foremost in the boat on the side of the turn.
This motion capture shows a buoy turn being taken mid race: