$100 – $250
An air pocket between the finish you touch (gel-coat or acrylic) and the fiberglass structure. A mould in the shape of the bathtub is sprayed with the top coat, then sprayed with the fiberglass. An air-pocket between the layers causes a void which can be revealed by pressure on the topcoat above the void, cracking like an eggshell.
It is repaired by removing the topcoat above the void, which can sometimes be quite larger than what is seen above, filling and fairing the void, and applying new topcoat.