The Mablethorpe bell is the only one mounted on a beach. It is fixed to large 'helical piles', which like large corkscrews are driven deeply into the sand; this is a common way of mounting structures on sand.
Anyone who has visited the bell may have noticed various levels of the sub-structure being revealed by shifts in the sand level. It seems that when the bell was installed the sand was at a relatively high level. but for various reasons it has changed: natural seasonal variations, the impact of large scale sand pumping just off shore, and more.
This necessitated some remedial work early in 2020.
But since then the level has risen. Time will tell where it ends up.....