To work at the beach in Engpsh, you can say "to work by the sea" or "to work on the coast." You can also say "to work at the beach," which means that you are physically working at a location that is on the beach or very close to the beach. For example, you might work at a beachfront hotel, a beachside restaurant, or a beach rental company. Alternatively, you can say "to work in the beach industry," which means that your job is related to the beach in some way, such as by providing goods or services to beachgoers or by working in a role that is related to the tourism industry.