Haikou

Descending into the Hai Shui Dao is a bit like entering a James Bond villain's lair-except you won't need tuxedos or secret handshakes. This audacious underwater tunnel connecting tropical Hainan island to mainland China's sleepy Xuwen district is an engineering stunt worthy of applause or at least a bemused raise of eyebrows. Completed after years of meticulous planning, this aquatic wormhole slices gracefully through the Qiongzhou Strait, offering surreal, kaleidoscopic views of sea life gliding nonchalantly past your window. Arriving early morning or late afternoon ensures vivid marine vistas minus the midday glare and crowds; book tickets online at least a week ahead to avoid the particularly aggressive queue-jumpers who see overcrowding as an Olympic sport. Budget at least 120 yuan ($18) per person, and don't roll your eyes at the security screening-it's thorough enough to rival airport TSA but with considerably fewer confiscated hair gels and mouthwashes. And bring your camera, or at least a phone fully charged-in these pristine, futuristic depths, your friends will demand pictorial evidence of your bizarre nautical commute. Even if a subterranean voyage through turquoise waters isn't exactly on your bucket list, the Hai Shui Dao tunnel journey offers bragging rights forever-or at least until Elon Musk builds something stranger.