The basic principle of nautical quartz clocks is that the period of the pendulum remains unchanged. the pendulum moves one cycle, and the second hand moves once or twice.
However, the waves will cause the pendulum to shake. in this process, the pendulum will be affected by forces other than gravity, the cycle will change, and the time will be inaccurate.
In order to make the pendulum of the "nautical quartz clock" receive the same force every time, the back of the pendulum is connected to a spring. every time the spring is stretched and compressed, the pendulum will swing synchronously with the same force to ensure that the second hand moves once.