Sea prune

The sea prune is a small, purplish colored vegetable which grows in the oceans. In traditional Water Tribe cuisine, they are dried and boiled, making a chunky brown stew which can be hard to eat for people unaccustomed to its taste. According to Hama, ocean kumquats are a lot like sea prunes.

Aang and Toph were not particularly fond of sea prunes.

Connections
The names of the sea prune and ocean kumquat are probably a reference to the sea cucumber, an echinodermic ocean-bottom scavenger which has been found to have 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. The prune and kumquat must be vegetables, since the vegetarian Aang was willing to try them, and Sokka or Katara would surely have warned him if they were not compatible with his diet.