Complex sentence: Jack survives the encounter and finds himself on Devil's Reef, where he discovers old smuggling tunnels beneath the seabed, leading him to the underwater city of Y'ha-nthlei.
Split into simpler sentences: Jack survives the encounter and finds himself on Devil's Reef. On Devil's Reef, Jack discovers old smuggling tunnels beneath the seabed and finds a tunnel leading to the underwater city of Y'ha-nthlei.