A shark (상어, sangeo) is read as danger and aggressive competition — decisive, fast-moving, and difficult to negotiate with, a notably harsher reading than most of the other sea animals in this category.
Being chased by a shark is read as facing a real competitive threat, most often in a professional or business context — a rival playing to win rather than simply competing. Successfully escaping a shark carries the same relief-based reading as escaping any pursuer elsewhere on this site: overcoming a serious, fast-moving threat rather than a minor obstacle.
Catching, taming, or otherwise gaining control over a shark is read as a notably strong, aggressive version of victory — not just surviving a dangerous rival, but genuinely gaining the upper hand over them, turning their own aggression into your advantage.
A shark seen calmly from a distance, without any direct threat, is read more mildly — awareness that dangerous competition exists somewhere nearby, without it currently being pointed directly at you.