Sinbad, a great sailor, sets out on a voyage to sail all the way to the end of the rainbow, but his greatest admirer, Pablo, sneaks aboard his boat as it leaves. He begs Sinbad to let him be his First Mate so he can help out during the trip, but his innocent clumsiness seems to be causing the legendary sailor too much trouble for the voyage. Will Sinbad the Sailor need the help of his first mate before the end of the voyage?
Tyrone is in the backyard, standing on the picnic table. He introduces himself to the viewer as Sinbad, a great sailor who sails the seven seas on a ship. He explains that he will sail all the way to the end of the rainbow as he sings I'm Sinbad the Sailor. The backyard transforms into a dock as Tyrone walks on to his ship. He begins to sail off.
A blue penguin, Pablo, runs to the ship and the ship stops. Pablo asks if he can help Sinbad sail. Pablo is actually an inexperienced sailor, but a huge fan of Sinbad. Sinbad does not accept his request. Sinbad begins to sail away. Pablo jumps aboard quietly so Sinbad does not notice and hides in a barrel of water. Sinbad sails the ship and walks to the barrells of water for a drink. He finds Pablo as Pablo asks him if he can help, and Sinbad calmly makes a deal with him: If Pablo is going to accompany him, he must do everything he says. Sinbad tells him that he can steer the ship. Pablo does his best, but accidentally causes the barrels of water to fall off the ship, and Sinbad as well! Once back on board, Sinbad becomes upset at having lost the water, and he tells Pablo that the only place to get some more is at the Island of the Siren.
They sail to an island, where Siren lives. They ask Siren for water, but Siren says that they cannot get water unless they beat her in a game of "Siren Says" (a version of the popular children's game known as Simon Says). She sings the song Siren Says as they play the game. She explains that, if she says "Siren says..." before a statement, the players do what she said. If she does not say "Siren says..." in front of a statement, and a player does it, they have to go back to the starting line. Whoever walks to the fountain of water first will win and get the water. Pablo wins and gets to fill the barrels of fresh water.
The two return to the ship and Sinbad tells Pablo that he can mop the ship. Pablo accidentally causes the crates of food to go falling off the ship. Sinbad angrily tells Pablo that they have to go to Medusa for get more food. They sail to an island and meet Medusa. She says that they cannot get her food unless they beat her in a game of freeze tag (a version of the game known as "tag"). To play, Medusa will chase the players, and if she tags one player, the player is literally frozen until another player taps them. Medusa sings Gotta Dodge as they play. Pablo is frozen first. Sinbad tries next. Pablo tricks Medusa into freezing herself by saying "What's that on your head?", causing herself to freeze her body. They get the food and get back on the ship.
Pablo wants to help Sinbad, but in the confusion Pablo drops the anchor of the ship, the ship stops and Sinbad falls in the water. Sinbad tells Pablo that he has to sit in a chair at all times because, if he doesn't, they could lose their food of water again. Sinbad starts to sing the song titled Do It Myself. Sinbad sees the rainbow and realizes that the ship is about to fall off a waterfall. Sinbad is about to fall off the ship and tells Pablo to get out of the chair and save him. Pablo does not accept because Tyrone ordered him to stay there. Sinbad wishes he hadn't said that, but tells Pablo to save him and adds "please" at the end. Pablo drops the anchor again and picks Sinbad up. Sinbad invites Pablo over to his house for a snack.
Pablo accepts as the ship transforms back into the backyard. Siren and Medusa join them as they sing the end song and enter Tyrone's house. Tyrone opens the previously closed door and shouts "Ahoy, mateys!" as the end credits start.