Undersea tunnels are dangerous until they are stabilized and lined, but once completed, they are safe as houses.海底隧道在没有砌好并加固前是有危险的，但是一旦完工，就十分安全。Hold onto my hand and you'll be perfectly safe.抓住我的手，你会十分安全的。Walkways allow visitors to enter the caves in perfect safety.步行道使游客可以十分安全地进入洞穴。