This is the next stage of the Cumberland Basin cleaning cycle. In the earlier pictures, you could see they'd emptied the basin. Now, with the Entrance Lock gates open, they sluice out the basin with an inrush of fresh water. This helps wash out accumulated silt and also freshens the water—it's usually done just before the occasional traithlon that takes place here, otherwise the swimmers would be even more at risk from E. Coli and other things than they are!
GPS Coordinates:
51.44817, -2.62198
Location: Spike Island