slack water

a period when a body of water is between tides.

water that is free of currents.

Origin of slack water

First recorded in 1760–70

Then we went down the river as far as the Elbow, where we waited in the slack-water to hail up-bound steamboats.

Raftmates |Kirk Munroe
No, sir; it's slack-water; or, rather, the ebb is just beginning to make.

The Two Admirals |J. Fenimore Cooper
Glen had swum and fished in it, and boated on it, until he knew its every current and slack-water pool.

Campmates |Kirk Munroe
It is high-water and slack-water, in Port Desire, at half-past twelve, on the days of full and change.

Narrative of the surveying voyages of His Majesty's ships Adventure and Beagle, between the years 1826 and 1836 |Robert FitzRoy

They fish around the 'slack-water,' catching the last of the ebb and the first of the flow, and hence drift but little either way.

The Hudson |Wallace Bruce

slack water

the period of still water around the turn of the tide, esp at low tide