Complex sentence: When the offspring is fully developed, they will stay inside the eggs in hibernation, and not hatch before the eggs have been flooded with water or may be triggered by a sudden drop in air pressure signaling an approaching storm.
Split into simpler sentences: When the offspring is fully developed, they will stay inside the eggs in hibernation until conditions are suitable. Hatching may be triggered when the eggs have been flooded with water or by a sudden drop in air pressure signaling an approaching storm.