She had earlier skied solo to the South Pole and hiked 2,600 miles alone across the United States.
Ms Kelty’s family have paid tribute to an “active and determined sister” and said the world was “a much smaller place” after her death.
Emma, who quit as head of Knollmead Primary in Surbiton, to travel was attempting a 4,000-mile solo kayak journey.
This would cover the source of the Amazon in Peru to its mouth on the Atlantic Ocean.
But a short time later she posted, “Today started fighting my paddling way through 20km of storms!”
Her final post, also on September 13, reads, “At 1am such a dramatic change in one day. but such is the river. every Km is different and just because 1 area is bad doesn’t mean next is”.
Kelty wrote on social media that in a Coari, a stretch of the river, she would have her boat stolen and be killed too. Her trip across the Amazon River continued and two days later she said she was in the clear. Searchers also are looking for her body in the river. In the post, she mentions that she turned the corner and found 50 guys in motor boats with arrows.
“My face must have been a picture! (Town was uber quiet. too quiet!) Ok 30 guys. but either way. that’s a lot of folks in one area in boats with arrow and rifles”.
A day later the adventurer vanished.
She set off a distress signal last Wednesday, but despite extensive searches by police and the navy, her body has not been found.
A similar kayak to hers was discovered nearby.
One of the men accused of killing the British kayaker Emma Kelty during her expedition down the Amazon tried to decapitate her with a machete, police have said.
They then slit her throat before molesting her and dumping her bullet-riddled body into the river in the village of Lauro Sodre in Brazil.
The suspect, whose mugshot was released by detectives today, was found hiding in bushes with a phone and a Global Positioning System tracker. Two smartphones, a GoPro camera and a tablet were the items that the group was trying to sell, according to the suspect.
Police confirmed afterwards the pirates went out in a canoe and targeted Emma at random when they saw her tent. Police said he was 19, not 17, as he had previously claimed.
A suspect, Evanilson Gomes da Costa, 24, later died after being shot by rival gangsters.
Another person arrested, a teenager, told investigators that Kelty was camping on Boieiro Island, located in front of a riverside community, when she was approached by the group.