It is a common misconception that fiberglass pools can "pop" out of the ground. This is often spread by some pool contractors who prefer other types of pool installations, such as gunite or vinyl liner, and use this as a scare tactic to steer potential customers away from fiberglass pools.
However, when installed properly, a fiberglass pool will not "pop" out of the ground. This type of installation is typically done by first excavating a hole for the pool and then placing the pool shell into the hole. The backfill material is then carefully placed around the pool, and the pool is secured in place with supports and braces to prevent it from shifting or moving.