It's been a deadly weekend on the waterways in southern and central Alberta.

Three men are believed to have drowned in separate incidents on Sunday.

The first happened just before 7:30 p.m. at Herbert Lake in Banff National Park when a man in his early 20s fell into the water while paddle boarding and didn’t resurface.

A search was launched immediately, which was unsuccessful and crews were expected to return to the area on Monday.

Sgt. Gerald Walker said the man was part of a group of seven people paddle boarding at the time.

“It appears right now that the person was not wearing a life jacket and was not a strong swimmer,” he said.

“Parks Canada visitor safety has a dive team in there searching for the person. There has been ground crews going around the lake to make sure they didn’t come out and now the dive team is there trying to locate the body.”

Walker said Herbert Lake is one of the warmest in the area, as it is not glacier fed, which makes it popular.

“Any of these lakes, make sure you know it’s cold water, if you fall in, it is a lot harder to swim in, make sure you prepare for that,” he said.

“Wear a life jacket and take all of those precautionary measures.”

Herbert Lake is about 180 kilometres west of Calgary.

The man’s identity has not been released.

The second happened about 8 p.m. near Okotoks when RCMP were called to the Nature's Hideaway Family Campground along the Highwood River for reports of a missing swimmer.

Police said a man in his early 20s jumped from a ledge into the water and was seen briefly before he went underwater and didn’t resurface.

He has been identified by friends as Lual Ayach, 22.

Several people who were in the area tried searching for Ayach without success.

The Calgary police HAWC helicopter was brought in, along with a Foothills Fire Department water rescue boat, however he was not located.

The Foothills Fire Deaprtment was searching the river as of 11:30 a.m. Monday and members of the dive team were preparing to enter the water.

Ayach was with friends celebrating the Canada Day long weekend in an area popular for swimming, said Const. Chantelle Kelly.

"it is very common for local people to go swimming and jump off the cliffs around there," she said.

"But what I'm being told is with the recent rise in water in the area, the current has been really strong and where people are jumping in has been very turbulent."

Searchers are focused on the area from the campground to where the Highwood River meets the Bow River.

Kelly said the man was not wearing a life jacket and was not a strong swimmer.

Alcohol is not considered to be a factor.

The third incident happened about 10:15 p.m. Sunday when Rocky Mountain House RCMP were called to the Clearwater River after witnesses reported seeing a man wearing a life jacket floating in the turbulent water.

He was last seen about 45 kilometres west of the Clearwater Bridge near Highway 22 and Highway 591.

Police said a truck and trailer registered to a man in Calgary were found nearby and they have not been able to contact him.

Searchers were not able to put a boat on the water due to the strong current and debris in the water.

And RCMP helicopter and search teams were brought in Monday.

(With files from CTV News Calgary's Alesia Fieldberg and Camilla De Giuseppe)