Sea glass
Collectors walk beaches to find sea glass. After plastic became popular for containers it became harder to find sea glass. Sea glass can take from 7 to 10 years to get a frosted appearance. In many places winter seems to be the best time to find sea glass. Experienced sea glass hunters look for periods of low tide to start looking. Beaches that are cleaned of debris regularly won't produce much sea glass. Hunters look for "dirty beaches" that are left alone and have litter.