A Hot Spring is a steaming pool of water that heals the protagonists in EarthBound and Mother 3. It takes 5-6 seconds to heal and refresh the entire party. They are free of cost.

Hot Springs from EarthBound

Interestingly, there are two Hot Springs located in Eagleland. These pink hot springs are found and used in Saturn Valley and Tenda Village. Since hotels and houses are used to heal Ness and co. to full HP and PP, hot springs are naturally used to cure all status ailments.

Hot Springs from Mother 3

Mother 3 makes extensive use of Hot Springs. These pools (all of these are filled with water, with the exception of the pink Hot Spring in Saturn Valley) are located almost everywhere in Nowhere Islands, from Osohe Castle to being in a present under the Empire Porky Building. Hot Springs play a much more significant role in Mother 3, since Lucas and co. can use them to not only still heal their status ailments, but also their HP and PP stats. This change is due to the fact that hotels do not play a significant role in Nowhere Islands. If a Fresh Egg is placed directly in the Hot Spring, the egg does not turn into a Chick, but instead becomes a Hot Spring Egg. There is also a sign next to the Hot Springs in Saturn Valley saying "Base was here". In Tanetane Island, when the party is hallucinating, the sludge in the island appears to be a hot spring and (surprisingly) recovers their HP and PP too (Except Boney since he did not hallucinate; he sat at the edge of the sludge pool).