The deaths occurred in the cantons of Zurich, Neuchâtel, Vaud and Bern, according to police and media reports.
A 44-year-old tourist from Thailand drowned in the Limmat River near Dietikon, northwest of Zurich, shortly after 4pm, Zurich cantonal police said.
The man and his 41-year-old companion were seen drifting past Werd Island before he sank, police said.
His friend swam to shore to get help.
Two helicopters, boats and police divers were engaged to search for the man, whose body was discovered 150 metres from the Dietikon power plant.
Zurich cantonal police and the public prosecutor are investigating the exact causes of the man’s death.
Meanwhile, Neuchâtel cantonal police issued a plea for information from the public after a 17-year-old boy drowned in Lake Neuchâtel on Tuesday at around 6.30pm.
The youth was swimming with a friend near a jetty at Neuchâtel’s marina, police said.
His friend was unable to safe the boy and efforts by emergency medics to revive him were unsuccessful.
Police are continuing to investigate the case.
The incident happened about an hour after another drowning in the same lake off a beach in Yverdon-les-Bains in the canton of Vaud.
Vaud cantonal police reported receiving a call about a man who was in distress while swimming about 100 metres from Yverdon’s “grande plage” at the western end of the lake.
Other bathers were able to pull the man to shore but efforts by ambulance attendants to revive him were unsuccessful, police said.
Police said efforts to identify the man were under way and the cause his death is being investigated.
Meanwhile, 20 Minuten reported online that a young man drowned in Lake Biel between 8 and 9pm.
The newspaper cited a witness who said the man was swimming in the lake near the Biel city district of Vingelz when he suddenly cried for help.
The man’s girlfriend reportedly jumped into the lake to save him but was unsuccessful.
20 Minutes said police divers recovered the man’s body around 10pm.
Police have confirmed a swimming accident but did not immediately release any details.