Dragalge is an aquatic Pokémon that resembles a common sea dragon. Its body is curved in a way that vaguely resembles the number three. Its sides are a light purple with slender vertical lines, while most of the rest of its body is a dull brown. There is a light purple patch on its face surrounding its red eyes. It has a tubular, upturned snout and on the back of its head is a thin appendage. On top of its head is a red, leaf-like crest with two brownish-green antennae. On either side of its body is a skinny, leaf-like appendage and its tailfin also resembles a large leaf. There are three small spikes along its back.
Dragalge is a territorial Pokémon that will spit poison at whatever trespasses on its territory. Its poison is strong enough to melt the hulls of metal tankers. As a result, it is said that ships sailing through the seas where it lives never return. It hunts by hiding itself in seaweed and then ambushing prey with a spray of poisonous liquid. However, it is known to coexist well with Dhelmise. Dragalge can create Dragon energy by absorbing the sunlight through the plume on its head.
Dragalge appears to be based on a leafy seadragon, but bears resemblance in shape and body appendages to the weedy seadragon. Both of these animals are capable of mimicking the appearance of aquatic foliage as a way of camouflage, like Dragalge. The Pokédex entries for Dragalge and its pre-evolution make several allusions to a diet, habitat, and resemblance based around rotten kelp, a kind of seaweed. Notably, rotting seaweed releases highly toxic gas, and can cause poisonings.