A man has died and two teenagers are missing in separate incidents after they went swimming in the hot weather.
The man was found in the Jubilee River in Slough but was pronounced dead at the scene.
Thames Valley Police say the death is not being treated as suspicious and the mans next of kin have been informed.
The 17-year-old boy, from Itchington, Warwickshire, is believed to have got into difficulty while swimming in Bishops Bowl lakes, at 6.30pm.
Rescue teams, including police, an air ambulance and firefighters, scrambled to the scene and were seen scouring the 90 acre former lime quarry.
The roads leading into the village have been closed as rescue teams battle to find the missing boy.
Meanwhile, in Essex, the coastguard was called at about 6.20pm to reports that two boys were in difficulty.
One boy was rescued by a lifeboat crew, checked over by medical teams and reunited with his family, but the second remains unaccounted for.
The search is expected to continue this morning.