Complex sentence: Having never learned to swim and ignoring the posted deep end signs, he ventured into the deep end of the pool, panicked and struggled before holding his breath, floating to the top and dog paddling to safety in the absence of a lifeguard.
Split into simpler sentences: Having never learned to swim and ignoring the posted deep end signs. He ventured too far into the deep end of the pool, panicked and struggled before holding his breath, floating to the top and dog paddling to safety in the absence of a lifeguard.