Two of the pals became trapped in quicksand under the water and the other three swam over to try and rescue them, the brother of one of the victims has claimed.
Ajirthan Ravi, brother of victim Nitharsan, 22, was told by doctors that his brother had died trying to save his two friends who were trapped beneath the water as the tide came in.
Nitharsan along with Kurushanth Anna, Indhushan Sri and brothers Ken and Kobi Nathan had driven to the popular beach spot to enjoy the hottest day of the year.
They got into difficulty while swimming – sparking a massive search-and-rescue operation as beachgoers watched in horror on Wednesday.
A sixth person is still missing, RNLI confirmed.
It is believed that the pals – all from south London – were playing football on a sandbar when they became trapped by rising water.
Pal Thujee Jay tweeted: "Why did God take 5 lives at once. RIP Nitharsan, Kuru, Kobi, Kenny and Indhusan. Can't believe you are all gone.
"I can't believe this. When going to the beach please don't go too deep. Lives are too precious to be lost due to silly actions."
Three were pulled from the sea at the stretch of coast near Rye, east Sussex at around 2.30pm.
Two more bodies washed up on the shore later that evening.
Police were able to indentify them using them by their car and their parents were told early Thursday morning.
RNLI confirmed that two more bodies had washed up on the shore taking the death toll to five.
Eyewitnesses recalled watching three men being pulled out of the water within minutes of each other on the hottest day of the year.
Emergency crew performed CPR for "half an hour" according to eye witnesses.
Search-and-rescue choppers as well as an air ambulance and RNLI were at the scene.
Police have yet to reveal the exact cause of death.
Several have questioned why there was no lifeguard on a beach packed visited by 25,000 sunbathers and swimmers.
One witness who declined to be named said: "The sea is very shallow for quite a long way. It seems so strange how they got into trouble. There was no waves and no wind."
Another eyewitness, Natalja Taylor, 30, who was on a day-trip with her husband, said police were driving up the beach with a loudhailer urging people to stay out of the sea.
She said: "We were sat on a hill a bit further away and we saw three people being pulled out of the water. I think the people who rescued them were regular people, not emergency personnel.
"We don't know what condition they were in. There were so many people there. They were still on the beach when we left.
"Police drove on to the beach with a loudspeaker, telling people not to go into the water until further notice. They also taped off a huge chunk of the beach so no-one could get near it."
Witness Bella Sanders said the incident was "shocking" for those on the beach.
She said: "One minute it was calm and then one person was pulled from the sea, then another, then another.
"It was shocking to see. The air ambulance arrived and were performing CPR on at least two of the casualties for at least half an hour."
The tragedy comes one month after a 19-year-old Brazilian tourist was found dead after being swept out on the same beach.
Gustavo Cruz was visiting family in Croydon when he was found dead on the shore.
The Sussex Police and Crime Commissioner has reassured members of the public that the authorities are doing everything they can to ensure people are safe following the tragic deaths.
