Surfers invented the wetsuit. No self-respecting surfer wears anything under their wetsuit except maybe an upper body rash guard. I've been using/wearing wetsuits for 20 years and would never dream of wearing anything underneath.
OK, but I live in North Carolina, I drive a Ford Escort, and there's not always a place to change or a wooded area near the beach. How do I get into the wetsuit modestly?
Maybe this was less of a concern for the California surfers who invented the wetsuit ;->
Jonathan