It follows a separate incident in West Mersea, near Colchester, on Wednesday in which a mother and her teenage daughter died.
Shally Rahman, 41, and Samiha Rahman, 15, tried to help a seven-year-old relative out of the water. He remains in hospital in a critical condition.
Ch Insp Stuart Austin, Clacton district commander, said: “I’m acutely aware there will be a sense of shock and worry given recent incidents elsewhere in north Essex in the last week.
“First and foremost, our thoughts are with those affected by the incident on the seafront yesterday.
“I’m also aware the area was busy, and the incident would have been seen by a lot of people.
“Emergency services were quickly on the scene, and all services worked incredibly professionally to clear the area to allow for medical professionals to help the three people involved.”
He urged people not to comment about the incident on social media.
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