A kind of porpoise · also called Harbour porpoise, Common porpoise

About
The harbor porpoise is one of the smallest marine mammals, reaching roughly the weight of a slender adult human.
It is one of the smallest cetaceans in the world, far smaller than most dolphin species. Unlike many other marine mammals, females grow slightly larger and heavier than males. Its compact, rounded shape minimizes surface area, which helps it preserve body heat in cold coastal waters.
From Wikipedia
The harbour porpoise is one of eight extant species of porpoise. It is one of the smallest species of cetacean.
Read more on Wikipedia →Text from Wikipedia’s “Harbour porpoise” article, CC BY-SA 4.0.
2 on the site
Weight
121 lb (55 kg)
Quick answer
A harbor porpoise is about 4.9 feet (1.5 m) long, 1.6 feet (0.5 m) tall, and weighs 121 pounds (55 kg). That makes it roughly the length of a park bench and light enough for two adults to lift.
Typical figures, the same ones every comparison on the site uses; real ones vary.
More like a harbor porpoise
Compare it
Next to anything: a person, a car, another porpoise.