CHICAGO (CBS) — High waves will make being on Lake Michigan dangerous for swimmers and boaters alike on Monday.

The National Weather Service has issued a beach hazard statement through 5 a.m. Tuesday, because of 4 to 8 foot waves and strong rip currents and structural on the lake.

The Chicago Park District has issued swimming bans or swim advisories at virtually every beach on the lakefront on Monday due to the rough surf.

A small craft advisory also has been issued through 11 p.m. Monday, due to occasional waves of up to 8 feet. Inexperienced boaters are advised to avoid going out on the lake.

Sailing instructor Capt. Jeff Harris said the high waves prompted some of his students to cancel their lessons on Monday.

“They must have checked the weather and just saw that there’s big huge waves out here,” he said.

Harris said boating in conditions like these comes with a major concern.

“Man overboard is our biggest concern, and whenever you’ve got big huge waves like this it’s hard to see the people when they go down in the troughs,” he said.

He said that’s why it’s simply safer to avoid sailing in such high waves.

“One of the things I look at as well, is you see if there’s any other sailboats out there. If you don’t see any, that’s a big huge telltale,” he said.

The Chicago Fire Department warned swimmers and boaters that conditions on the lake can change in an instant. They made multiple rescues on the lake over the weekend.

One man died and another was hospitalized Saturday afternoon, after they jumped off a boat near Diversey Harbor to go for a swim. Their boat started drifting away, and they weren’t able to make it back.

Rescue crews pulled both men from the water. One victim, 31-year-old Jose Rubio, was taken to St. Joseph Hospital, where he was pronounced dead. The other victim, a 28-year-old man, was taken to Advocate Illinois Masonic Medical Center, where his condition was stabilized.

Fire officials said there were seven or eight more water incidents on Sunday. They noted very high water levels in the lake have made the lake more dangerous than usual.

“We have had a lot of water rescues this year, because of the high water levels. Some things that used to be able to be seen are now under water,” Deputy Chief Jason Lach said. “Lake Michigan is just a small ocean, alright? Conditions change rather quickly. The wave conditions pick up very fast, and can make it difficult for even an experienced boater or swimmer.”

Meantime, in northwest Indiana, a 25-year-old man was in critical condition after firefighters pulled him out of the lake from Washington Park Beach in Michigan City. He had been swimming with his family when he went under the surface and didn’t come back up.

The man was being treated at Franciscan Health Hospital in Michigan City, Indiana.

According to the Great Lakes Surf Rescue Project, 20 people have drowned in Lake Michigan this year.

The waves on Lake Michigan are expected to diminish overnight.