He had three ways of traveling to the other city. By air(:)(,) flying in his private jet. By land (:)(,) driving his truck. By sea (:)(,) taking the town's ferry.
What's the correct punctuation in this case and why?
You have a list (containing three items), where each item contains a comma, so use semicolons to separate the list items:
He had three ways of travelling to the other city: by air, flying in his private jet; by land, driving his truck; and by sea, taking the town's ferry.