An ocean kumquat is a small, round fruit often consumed in the Fire Nation. It is similar to the sea prune in flavor and consistency, but contains much more protein and iron, making it ideal for storage aboard ships for long ocean voyages.
After Team Avatar discovered Hama was from the Southern Water Tribe, she insisted on cooking a traditional Water Tribe meal for them. Unable to gather all the required ingredients in the Fire Nation, she used ocean kumquats as a substitute for the traditionally-used sea prunes, commenting that ocean kumquats were similar to sea prunes if stewed long enough. Aang, however, showed overt reluctance in trying the kumquats, given his previous bad experience trying sea prunes, and promptly warned Toph against them.
The names of the sea prune and ocean kumquat are likely references to the sea cucumber, an echinodermic ocean-bottom scavenger which has medicinal properties, and is considered an aphrodisiac in the Far East due to certain aspects of its appearance. However, the sea cucumber is an animal, not a vegetable. Ocean kumquats are reminiscent of seaweed, with a bulbous end resembling a kumquat. Both amalgamations are edible on a vegetarian diet, as they do not contain any animal product or by-product.