Four college students have kayaked 200 miles (321km) to raise awareness of water pollution.
The team of water sports enthusiasts from Gloucestershire began their 9-day challenge to kayak the length of the River Thames on 13 July.
They reached their final destination in Canvey Island, Essex, on 21 July.
Stuart Williams, head of outdoor at Cirencester College, accompanied the group. He said: “The students proved themselves. They nailed it.”
The idea was a collaborative effort which came to fruition after several years of planning, he said.
Mr Williams, who developed a passion after studying environmental sciences, said he wanted “to pass those values on to the students I teach.”
“Having seen a few things in the media we wanted to support this and raise awareness. I feel like we’ve regressed a bit”, he added.
The group travelled in five kayaks from the source of the Thames near Coates in Cirencester.
Their journey began on foot, carrying the kayaks for the first 11 miles (17.7km).
As they kayaked the remaining 189 miles (304.1km) along the river, the students collected water samples to work out which sections of the Thames are the most polluted.
The samples will be tested for traces of nitrate and phosphorus, two substances that show up in high levels if water is polluted.