If you venture too far out of your depth it helps to have an Olympic swimmer nearby.
Newlywed Andrea Benedetto was drowning off a Sardinian beach on Sunday when Italian swimmer Filippo Magnini dived in to rescue him.
Magnini, a former world champion, plunged in after friends of Mr Benedetto shouted to sunbathers on Cala Sinzias beach, just east of Cagliari.
Magnini kept Mr Benedetto's head above water until lifeguards arrived.
"I just did what I had to," the retired sportsman said later.
Mr Benedetto, 45, had married his boyfriend two days earlier at a ceremony in Cagliari.
The aftermath of Sunday's incident was witnessed by a friend of the couple and BBC Persian journalist, Soroush Pakzad.
The pair were floating on an inflatable unicorn when Mr Benedetto fell into the water, which was colder than expected, and he was unable to move his limbs due to a medical condition.
A strong wind blew the inflatable away, Mr Pakzad explained, and Mr Benedetto's husband was left trying to keep his partner's head above water.
His friends' cries for help were heard by lifeguards, who raced to set off in their rescue raft. But 37-year-old Magnini, 1.88m (6ft 2in) tall, was closer and quickly reached the struggling man.
"The bather was in a lot of trouble: he was quite frightened, he was really stuck and had swallowed some seawater," Magnini said, quoted by Italy's Corriere dello Sport.
"When I reached him he wasn't even able to speak, and it wasn't easy to lift him on to the raft, so we laid him on an airbed that some other bathers had nearby."
Mr Benedetto was taken to hospital shortly afterwards. "When I became conscious my first thought was about my husband," he said.
"A few hours after the accident I was at the hospital when I realised that Filippo Magnini was the man who saved my life but I didn't have any chance to thank him as I have no contact with him. I hope to be able to thank him in person."
Magnini was on the beach with his girlfriend Giorgia Palmas, a well-known Italian TV celebrity and model.
Magnini was in Italy's 4x200m freestyle relay team which won bronze in the 2004 Athens Olympics.
He was also world champion in the 100m freestyle in 2005, and retained that title in 2007 when he tied with Canadian Brent Hayden for gold.
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How to spot someone drowning
There is such a thing as the "Instinctive Drowning Response" which, experts say, gives little indication that a person is drowning. That response means they do not usually thrash around.
Survival experts Mario Vittone and Dr Francesco Pia, writing in the US Coast Guard journal On Scene, say:
- Except in rare circumstances, drowning people are physiologically unable to call out for help. The respiratory system was designed for breathing, so speech is secondary
- Drowning people's mouths alternately sink below and reappear above the surface of the water. Their mouths are not above the surface long enough for them to call out; they exhale and inhale quickly as they start to sink
- They cannot wave for help - nature instinctively forces them to extend their arms laterally and press down on the water's surface
- The response keeps their bodies upright in the water, without any supporting kick
- They can only struggle on the surface for 20-60 seconds before sinking.