The Road to El Dorado

In Spain 1519, two con artists, Tulio and Miguel, win a map to the legendary City of Gold, El Dorado, in a rigged gambling match. After their con is discovered, the two evade capture and hide aboard one of the ships to be led by HernÃ¡n CortÃ©s to the New World. During the trip, they are caught as stowaways and imprisoned, but manage to break free and take a rowboat with the help of CortÃ©s' horse, Altivo.
Later, they land on an unknown shore at the edge of Mexico, and Miguel begins to recognize landmarks from the map, leading them to a totem marker near a large waterfall. Believing it to be a dead end, they suddenly encounter a native woman being chased by guards; when the guards see Tulio and Miguel riding Altivo as depicted on the totem, they escort them to a secret entrance behind the falls, along with the woman, and into a city truly made of gold, El Dorado. They are brought to the city's elders, kind-hearted Chief Tannabok and wicked high priest Tzekel-Kan. Tzekel-Kan, seeking to seize the city from Tannabok, insists that the two, mistaken as gods, demonstrate their powers. Tulio and Miguel bicker between themselves, while a nearby volcano begins to erupt. When Tulio yells at Miguel to stop pestering him, the volcano suddenly stops erupting, and the citizens take this as proof of their godhood. Celebrations are held, and the pair are given luxurious quarters to stay, along with charge of the woman, Chel. Chel is aware the two are conning the people but promises to remain quiet if they take her with them when they leave the city. The two are showered with gifts of gold from Tannabok, but disapproves Tzekel-Kan in sacrificing a civilian as the gods' ritual.
Tulio convinces Tannabok to build them a vessel that will allow them to leave the city with all the gifts they've been given, which will take three days. Miguel explores the city, allowing Chel to get romantically close to Tulio. Miguel comes to appreciate the peaceful life that the citizens seem to enjoy, and joins in with some of their activities. When Tzekel-Kan sees Miguel playing a ball game with children, he insists that the gods demonstrate their powers against the city's best players in the same game. Tulio and Miguel are far outmatched, but Chel is able to substitute the ball with an armadillo named Bibo, allowing them to win; Miguel spares the ritual of sacrificing the other team, much to the crowd's approval. During the match, Tzekel-Kan sees Miguel receive a small cut and realizes the two are not gods, because gods don't bleed. Tzekel-Kan conjures a giant stone behemoth to chase them through the city. As Tulio and Miguel argue over their differences, they manage to outwit the behemoth, causing both it and Tzekel-Kan to fall into a giant whirlpool, thought to be the entrance to Xibalba. When Tzekel-Kan comes to, he finds himself facing CortÃ©s and his men; thinking CortÃ©s is a god, he offers to lead them to El Dorado.
With the boat completed, Miguel states his intention to stay in the city. Tulio and Chel board the boat, loaded with the gifts, when they see smoke on the horizon and realize CortÃ©s is close. Tulio concocts a plan to use the boat to ram pillars under the waterfall to cave-in the main entrance to El Dorado, but this requires the citizens to pull over a statue in the boat's wake to give it enough speed to ram the pillars. As the statue starts to fall too quickly, Tulio has difficulty in preparing the boat's sails. Miguel, giving up on staying in the city, rides Altivo then jumps onto the boat to unfurl the sails, assuring the boat clears the statue in time. Tulio's plan works, though the boat and their gifts are lost. Tulio, Miguel, Chel, and Altivo end up near the totem and hide as CortÃ©s' men and Tzekel-Kan arrive. When Tzekel-Kan finds the entrance blocked, CortÃ©s accuses him as a liar, and Tzekel-kan is taken prisoner as they leave. Tulio and Miguel, though disappointed they lost their treasure, take off in a different direction for a new adventure with Chel, unaware that Altivo still wears the golden horseshoes he was outfitted with in the city.

Question: What does Tulio convince Tannabok to do?
Answer: build a vessel