Why doesn't Sam's Club in China sell live seafood? Sam's Club usually has a sign that says that deep-sea cold-water fish, which survive in shallow water, may require the addition of seawater crystals and antibiotics. Therefore, they only sell ultra-frozen seafood at -18°C. This is because seawater crystals contain a lot of heavy metals and industrial salt, which are used to dilute seawater. In order to keep the fish alive longer, a large amount of antibiotics is often added. Long-term consumption of such seafood can cause significant harm to the human body.