Which pairs belong near water

Wet tile is the hardest surface a sandal deals with, and most of what makes a pair good on it is invisible in a product photo.

Grip is a pattern, not a material

Rubber alone does not grip when there is a film of water between it and the floor. What works is a tread with somewhere for the water to go: channels that run to the edge of the sole rather than a shallow decorative texture in the middle. Turn a sandal over before you buy it for a pool.

The top layer matters as much

A wet foot slides on smooth plastic. The mat layer keeps a slight tack when it is wet, which is the difference between walking normally and gripping with your toes all the way to the towel.

What water does over a season

• Chlorine fades dyed straps and makes light EVA go chalky. Rinse in fresh water when you get home; that is the whole maintenance routine.
• Salt dries into crystals inside the strap holes and works like sandpaper from the inside. Same fix.
• Sun is worse than either. A sandal left face-up on hot concrete every day for a summer will harden and crack before the water gets a chance.

What should not go near a pool

Anything plush, and anything with a suede or leather upper. A lining that gets soaked dries flat, stiff and eventually smells. Keep those for the hallway.