The bright, blue-green film piling up in the canal in Jason Pim’s backyard is the first thing he wakes up thinking about and the last thing before his head hits the pillow.

The pungent odor of the algae, which has traveled dozens of miles from Lake Okeechobee, Florida’s largest freshwater lake, is hard to describe. But Mr. Pim, 37, said the smell is like opening a bag of moldy bread.

“To just watch it in the water and kind of just lap up and down with the water is a pretty eerie sight,” he said on Sunday. “It’s kind of mesmerizing.”

An unusually large algae bloom has filled the lake with a pea soup-like mixture that has built up because of rain, hot weather and a heavy concentration of phosphorus and nitrogen from fertilizer, Richard P. Stumpf, an oceanographer with the National Oceanic and Atmospheric Administration, said.