Here are a few possibilities depending on the criteria:
* The frilled shark has the most fins by name: It has two dorsal fins, two pelvic fins, two pectoral fins, a single anal fin, a single caudal fin (tail), and two tiny, extra fins called precaudal fins** located before the tail.
* Some fish with many tiny finlets: Certain fish like tuna and mackerel have numerous finlets along their dorsal and anal fin, effectively increasing their fin count.
* Fish with complex fin structures: Fish like sea horses have specialized fins hidden within their body, adding to the overall complexity.
Ultimately, the answer is dependent on how you define a fin. While the frilled shark has the most distinct fins with individual names, other fish might have more total fin structures if you include smaller, specialized fins.