Plot: Charlie Barkin, Sasha La Fleur-Barkin, and Jazz Barkin wanted to go on a merdog vacation with Itchiford "Itchy" Dachshund, Winifred Bessimay "Bess" de Winkerville, and Queen Annabelle of kindness, music, and love. On their vacation, they'll have fun in the bigger blue lagoon where they happily swimming and playing in the waters, dine-in at the underwater tropical calypso restaurant, having underwater spa, and also build sand castles on the beach. But whenever Carface Carruthers and Killer noticed that Charlie and Itchy were merdogs, They decided to join Belladonna and Madame Mousey for an evil scheme to deal with them. Belladonna turns them into merdogs to steal the seashell-themed horn of the Merdog kingdom so they can summon Red the sea demonic feline creature (which was half demon cat, half devilfish/manta ray) to destroy Sasha and Charlie forever that it may be a trap for the merdogs. Would the Barkin Merdog family get to safety and had any chance to defeat Belladonna and Red? Find out what happened...
- Evil Manta: Red (from All Dogs Go to Heaven 2); A sea demon
- Extra 18: Carface Carruthers (from All Dogs Go to Heaven)
- Extra 19: Killer from (All Dogs Go to Heaven)
- Extra 20: Pongo (from 101 Dalmatians); Dalmatian merdog
- Extra 21: Patch, Lucky, Penny, Rolly, and other 11 Dalmatian siblings (from 101 Dalmatians); Dalmatian merpuppies