00:00Underwater tunnels breathe like living things.
00:03Scientists found why.
00:06Even deep underwater, tunnels can grow and shrink by over a meter.
00:11Cars and lights make them warm, then ocean cold makes them pull back.
00:15Without special joints, the concrete would crack and burst apart.
00:20Discover more secrets engineers hide inside.
00:23Check the link in bio.
