A human diver is easily dwarfed by adult billfish. The largest species can reach 15 feet in length.

Black Marlin

The record-breaking black marlin that Alfred C. Glassell, Jr. reeled in off the shore of Peru in 1953 was 14.5 feet long and weighed 1,560 pounds. However, it is believed that the longest black marlin in the sea could reach 15 feet. Black marlin are dark blue on the back, and their bellies are a silvery white. All “granders,” or marlin weighing over 1,000 pounds, are female.

Sailfish

Slimmer and shorter than marlin, sailfish have a long, rounded spear extending from the snout. The largest known sailfish reached 11.4 feet in length. They are distinguishable by their dark backs, silvery bellies, and elegant dorsal sail.

Swordfish

Swordfish are slender and scaleless. Unlike sailfish, the “sword” extending from the swordfish’s snout is flat — not rounded. Swordfish are bluish on the back, sometimes with a purple sheen, and silvery below. While the very largest among them may reach 15 feet in length, a 7-foot-long swordfish is considered very large.