Silver/silvertone Sea Creature Charm Necklace

Sea creature necklace has a traditional claw clasp which is adjustable from 18-22.5”, but also has a secondary “clasp” for quick on and off—a dolphin goes through the loop holding the other charms (sea turtle, starfish, sand dollar, and pearl). I’m not sure if this is silver or just silvertone, but there is a slight tarnish to the chain and the charms so I believe there is silver content, although I see no markings.