Mesh pool cover
Also called: mesh winter cover, mesh safety cover.
A mesh cover is a pool cover that lets rain and snowmelt drain through it, so there is no standing water to pump and no weight load building on the cover. The price is a dirtier spring opening, because fine debris and some sunlight get through.
Why it matters
For most in-ground pools, a mesh safety cover is the short answer; choose solid only if a spotless spring opening is worth managing water on top all winter. A mesh cover is a safety cover only if it says so: a genuine one anchors into the deck and is certified to ASTM F1346. At the premium tier, Loop-Loc's Super Dense Mesh is marketed as blocking virtually all sunlight while still draining. On an above-ground pool no mesh cover is a safety cover, solid is the default, and mesh drains slowly, not instantly; owners cinch it tight through the grommets with bungees so it cannot sag and pond.
In numbers
Loop-Loc sells its Aqua-Xtreme as a light-blocking mesh that still drains up to 80 gallons per minute. That is the maker's claim, and it is why the question to ask a dealer is how much light a fabric blocks and how it sheds water.