Complex sentence: Much of the interior land mass at that time was a tangled jungle of mangroves, and clearing it, deepening channels and water bodies, and eliminating native growth almost everywhere in favor of land fill for development, was a herculean effort.
Split into simpler sentences: Much of the interior land mass at that time was a tangled jungle of mangroves. Clearing it, deepening the channels and water bodies, and eliminating native growth almost everywhere in favor of land fill for development was a herculean effort.