Water that turned the earthen mound into an island had receded enough for horses and rescuers, including veterinarians, firefighters and animal welfare officers, to wade out to the stranded animals, local mayor Wil van den Berg told reporters.
The plight of the stranded horses has fascinated the country, which has followed the rescue attempts on television and in newspapers since a storm surge early Tuesday pushed sea water into the wilderness area outside the dikes of Marrum, a town 145 kilometers (90 miles) northeast of Amsterdam.
One horse died Thursday night, a veterinarian said, bringing the total number of animals killed from drowning or exposure to 19. Rescuers planned to use other horses to lead the panicky animals, including several foals, back to dry land Friday.
"We plan to mark out a safe track through the water," which was less than a meter (3 feet) deep in most places, but up to 2 meters (6 feet) deep where the surrounding fields are crisscrossed with drainage channels, van den Berg said.
The channels, along with submerged barbed wire fences, are difficult to see in the brackish flood waters, hampering rescue efforts, reports AP.
Once the track about 600 meters (650 yards) long has been staked out, rescuers on horse back and firefighters, some in small boats, will head out to the animals and lead them back to a dike, where they can rest before being led to a dry pasture, van den Berg said.
By early afternoon, six 'guide' horses with riders had waded out to join the herd, preparing to get the operation underway.
Rescuers have been feeding the animals with hay and giving them fresh water to drink to keep up their strength.