Archies Flip Flops are all open toed, water can get on-top of them. However, in terms of water getting inside them, as the flip flops are all one piece foam construction and do not contain any fabric or glued parts, the flip flops are waterproof, water cannot get inside them and does not damage them.
When walking in wet conditions, Archies Flip Flops usually have great grip, however, they are not non-slip. The grip that we use is the herringbone pattern. It's a really good grip and it's the grip that is used in most tennis shoes for use on clay courts and skateboard shoes, both sports that require top grip! This grip has good abrasion resistance and in our experience, does not readily wear down unless you are really heavy on your feet and doing really high miles or have had the flip flops for a long period.
Our advice when wearing the flip flops on slippery surfaces is the same that I would give to someone wearing any type of footwear on a wet and slippery surface, slow down and be extra careful!