Nearly two thousand people took part in the Great East swim - among them two Olympic swimmers who are hoping to go for gold in the open water events at London 2012.
Russell Hookey spent the day at Alton Water near Ipswich and saw the action:
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This afternoon could see some heavy and thundery showers. Away from the showers though some warm sunny spells are likely. Highs of 25 deg C
I Am Team GB is offering all kinds of free activities across the region - all with the aim of encouraging more people to get active.
A rather cloudy start with showers likely in places. These could turn heavy and thundery, especially by the middle of the day.