Bottle Nose Dolphin vs Atlantic Blue Marlin

They are grey, varying from dark grey at the top near the dorsal fin to very light grey and almost white at the underside. This countershading makes it hard to see, both from above and below, when swimming. Adults range in length between 2 and 4 meters (6.6-13 ft), and in weight between 150 and 650 kilograms (330- 1,400 lb). Males are on average slightly longer and considerably heavier than females. In most parts of the world, the adult's length is about 2.5 m (8.2 ft), with weight ranges between 200 and 300 kilograms (440 and 660 lb). Their size varies considerably with habitat. Except in the eastern Pacific, dolphins in warmer, shallower waters tend to be smaller than those in cooler pelagic waters. A survey in the Moray Firth in Scotland, the world's second northernmost dolphin population, recorded an average adult length of just under 4 m (13 ft) compared with a 2.5 m (8.2 ft) average in a population off the coast of Florida.
Bottlenose dolphins can live for more than 40 years. However, one study of a population off Sarasota, Florida indicated an average lifespan of 20 years or less.

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The biggest females are more than four times as heavy as the biggest males. Males rarely exceed 160 kilograms (350 lb) in weight, and females commonly weigh over 540 kilograms (1,200 lb). The longest females can reach a length of more than 4 meters (13 ft) with the bill, from eye to tip, constituting about 20% of the total body length. Both sexes have twenty-four vertebrae, of which eleven are precaudal and thirteen are caudal.

This marlin has two dorsal fins and two anal fins. The fins are supported by bony spines known as rays. Its first dorsal fin has 39 to 43 rays from front to back. Its second dorsal fin has 6 to 7 rays. Its first anal fin, which is similar in shape and size to the second dorsal fin, has 13 to 16 rays, and the second anal fin has 6 to 7 rays. The pectoral fins, which have 19 to 22 rays, are long and narrow and can be drawn in to the sides of the body. The pelvic fins are shorter than the pectorals, have a poorly developed membrane, and are depressible into ventral grooves. Its first anal fin, along with its pectoral and caudal fins, can be folded into grooves. This streamlines the fish and thereby reduces drag.

The body is blue-black on top with a silvery white underside. It has about fifteen rows of pale, cobalt-colored stripes, each of which has round dots and/or thin bars, located on both sides of the fish. The first dorsal fin membrane is dark blue or almost black and has no dots or marks. Other fins are normally brownish-black, sometimes with a hint of dark blue. The bases of the first and second anal fins have a hint of silvery white. Marlin can rapidly change color and usually appear bright blue when hunting. The coloration results from pigment-containing iridophores and light-reflecting cells. The body is covered with thick, bony, elongated scales that have one, two, or three posterior points, with one being the most common form.