Dragalge is an aquatic Pokémon that resembles a common sea dragon. Its body is curved in 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 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.