A man had to be rescued after becoming stuck up to his neck in mud with the tide coming in, the Coastguard said.
At 11.20pm on Sunday, Solent Coastguard received a 999 call from a 13-year-old girl reporting that her brother and his friend were in trouble in the water off Portsmouth.
Coastguard rescue officers, police and ambulance crews were scrambled to the scene between Tipner and Whale Island where they found that an 18-year-old brother had made it ashore but a 21-year-old was still stuck.
The police helicopter was used to light up the area with its searchlight and a coastguard rescue officer entered the water to rescue the man who was stuck up to his neck in the water.
The two men were taken by ambulance to the Queen Alexandra Hospital while three others, two 13-year-old girls and a 19-year-old man, were dealt with by the police.
Steve Duff, Portsmouth Coastguard sector manager, said: "The coastal land at Tipner is subject to tidal conditions and when the tide is out leaves a large area of mud.
"It is strongly advised to keep clear of this mud. As we see from this incident, you can very quickly find yourself in trouble.
"Our Coastguard rescue officers are fully trained in coastal water rescue and had to put that training to good effect in this incident."