Save the Mermaid Kingdom

 is the fifteenth episode of "Backyardigans x Frontyardigans" written by Hornean.

Plot
Captain Andrew and his crew journey in the undersea vehicle to study the underwater activities. But soon they heard a call for help from two mermaid sisters (Uniqua and Denise). They took them to the Mermaid Kingdom where King Austin tells them that a series of quakes is threatening the kingdom. Can Andrew and his crew find out what's causing the shaking?

Characters

 * Andrew (Captain Andrew)
 * Thomas (Lieutenant Thomas)
 * Martin (Medic Martin)
 * Pablo (Scientist Pablo)
 * Tasha (Photographer Tasha)
 * Henwen (Engineer Henwen)
 * Sophie (Gardener Sophie)
 * Victor (Chef Victor)
 * Moe (Professor Moe)
 * Austin (King Austin)
 * Uniqua (Mermaid Uniqua)
 * Denise (Mermaid Denise)
 * Tyrone (Vizier Tyrone)

Songs

 * "Swimming, Swimming"