The Fastfin is an aquatic species of dragon introduced in the series, Dragons: Rescue Riders.

Physical Appearance:

Hatchling to Adult
The Fastfin is a four-legged medium-sized dragons. It has a long neck, thin body and an eel-like tail, which makes it perfectly adapted for an underwater environment. It has a crown of triangular shaped spikes on its head and small peg-like teeth.

The dragon has webbed feet, which helps it while swimming, but lacks claws. It has bigger front legs that back legs and a long, thin tail. It has two relatively small wings, which are better suited for swimming than flying.

Abilities:

Water Breath
Fastfins are capable of breathing streams of water. The water streams are powerful enough to push a heavy dragon a few meters away, or push a sheep up a cliff. The blasts are also very accurate. Fastfins are implied to store this water in their stomachs or other digestive system organ.

Swimming
Being a water dragon, Fastfins can stay underwater for long periods of time. According to Summer's description, she is also very fast. While Swiftwings are said to be the fastest dragon in the air, Fastfins are the fastest in water.

Immunity to Eels
Unlike most dragon species, Fastfins are one of the few specimens who don't have a fear of eels.

Immunity to Slinkwing Slime
Slinkwing slime doesn't stick to the scales of Fastfins, which Leyla suggested it is due to the dragons being aquatic.

Intelligence
Fastfins are very intelligent dragons, as seen with Summer, who is able to analyse natural phenomenons, such as wind currents, and come up with elaborate plans and ideas.

Prehensile Tail
Fastfins have prehensile tails. Their tails are also very powerful.

Endurance and Stamina
Fastfins can use their wings to block fire blasts from other dragons.

Weaknesses:
Illness
Like other dragons, Fastfins are susceptible to the contagious Dreaded Dragon Flu.

Behaviour and Personality:
Fastfins do not get scared easily.