Thousands of fish are to be moved as part of the first draining of the Union Canal for decades.
A three-mile section near Linlithgow will be emptied of water to repair leaks and remove obstructions.
Scottish Canals is staging two open days to enable people to see a normally-hidden aspect of the 200-year-old canal.
The operation started yesterday and will continue until 16 February.
A total of 30,000 cubic metres of water is being removed - enough to fill 12 Olympic-size swimming pools.
The fish - mainly tench, perch, roach and pike - will be caught with net and electro-fishing.
They will be transferred to holding tanks and released into adjacent sections of the canal.
Water will be drained using a valve at Woodcockdale, west of the town, following temporary dams being set up at Woodcockdale Bridge, Preston Road Bridge, Manse Road Bridge and Wilcoxholm Bridge.
The open days will be held from 1-3pm on Tuesday, 17 January and Saturday, 4 February, when Scottish Canals engineering, environmental and heritage experts will be on hand.
The section is the longest to be drained for at least 40 years.
Shorter stretches in the area were drained in the mid-1990s.
The canal, which connects Edinburgh with the Forth & Clyde Canal in Falkirk, was opened in 1822.
Infrastructure director Richard Millar said: “The 200-year-old Union Canal is a much-loved asset that attracts more than 10 million visits each year from everyone from boaters and cyclists to joggers and walkers.
“However, many of them visit the waterway without ever seeing all the hard work that goes on behind the scenes, and below the waterline, to look after the heritage, engineering, and habitats of this scheduled monument.
“The project we’re undertaking at Linlithgow is a fantastic chance for the public to see the scale of work that goes into caring for the incredible infrastructure of the Union Canal.
“They will be able to glimpse the craftsmanship of the waterway’s 18th century design as it exists below the waterline, and take a tour of the canal’s history, engineering, and habitats led by the people who know it best – our passionate and knowledgeable engineers, environmental scientists, and heritage experts.
“We may be their custodians, but these canals belong to the people of Scotland and are there for everyone to enjoy.
“I’d encourage everyone to come along to the open days to see the Union Canal as they’ve never seen it before and learn more about the hard work we undertake to care for the built and natural heritage of this amazing asset.”
Lowland Canals Volunteer Group chairman Ronnie Rusack said: “This will help because there have been leak problems for some time.”