What does multi-way mean here?

The beaded strand and the chain strand can be worn together as a layered look or styled on their own, depending on how the piece is put on. It gives you layered and single-strand options from one necklace.

What does water resistant mean for this necklace?

The maker describes it as water resistant, so light contact with water is less of a concern than with untreated costume jewelry. It is not stated as waterproof, so take it off for swimming and long soaks.

How long is it and can the length change?

It is listed at 16 to 18 inches, so it sits around the collarbone to just below it. The adjustable range lets you choose a closer or slightly lower fit.

The material and plating are not specified. Ask the seller for the metal and bead composition if you have sensitivities, since water-resistant claims do not identify the base metal.

Can I wear it with a pendant?

The chain layer can carry a small, light pendant if it has an opening clasp, but the beaded layer is best left as is. A heavy pendant may pull the fine chain out of shape.