Matt West, Watch Manager at Solent MRCC, said: "If you are heading out for a swim, check the sea conditions and remember that even though the sea may look calm on the surface, there is the danger of strong currents underneath.
"Always check tide times as well so that you can avoid being cut off by the incoming tide.
"If you see someone in difficulty, you should call 999 immediately and ask for the Coastguard."
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Thursday's weather for the west of the region
Thursday's weather for the east of the region
The RMT union has accused Southern of inventing figures which the company claims show record numbers of guards are going sick.