Remora fish attach to fish underwater, and they often have to hang on while they move at high speeds. This could be applied to submarines which could attach to ships in order to refuel and resupply without surfacing and exposing themselves.
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Tendons anchor to bones using a material hardness gradient that allows for the joint to handle more sudded stress witohout
tearing. This connection could be used in construction to make more durable connections in suspension bridges.
The leatherback sea turtles trachea is designed to partially collapse to handle increased pressure at deeper depths. This could be applied to submersible drones.