Byssal threads are strong, fibrous structures produced by certain marine organisms, particularly mollusks like mussels. These threads allow the organisms to anchor themselves securely to surfaces such as rocks, piers, and other underwater structures, providing stability in turbulent waters. The threads are made of proteins and are secreted by a gland in the foot of the mussel. Byssal threads are not only essential for the mussel's survival but also play a role in the ecosystem by helping to create habitats for other marine life.