penetrating sealer will prevent water from being absorbed and also allow limestone to release any built up moisture. Unsealed surfaces with absorbed moisture can result in efflorescence being deposited on the surface as the moisture evaporates.
penetrating, impregnating sealer travels below the surface of the stone or masonry surface, filling in voids and eliminating water migration, thus preventing the salt build up in the stone.
A deep penetrating sealer won't affect the slip resistance of your surfaces

will penetrate right into the pore structure creating a deep water resistant barrier which will be more effective at keeping out water and any dissolved salts.
Topical coatings which block the pores should be avoided. They can trap water inside the material and make the surface dangerously slippery when wet.

Limestone is perfect for use around pools in many ways – it looks good, feels soft underfoot, and doesn't become too slippery when wet or too hot under the sun. As salt can erode your stone, it is crucial to understand how to care for your limestone in a wet or salt-water environment.
