The Wedding Ship appears to be a combination of a galley and a barge or it could be a galley with the masts and sails removed. It has a bank of oars on both sides of the ship. The deck has been fitted with a rectangle canopy to cover the guests. The Ship is also equipped with lifeboats.
The only part of ship's interior seen in the movie is the bride's room in the back of the ship. It is a well decorated room with a large vanity, candelabras, and ornate curtains lining the room.
The ship is first seen as the vessel for Eric and Vanessa's wedding on the third day of Ariel's time as a human. It departed just before sunset and managed to get a good distance away from the shore when Scuttle first discovered Vanessa's true identity as Ursula, the sea witch.
The wedding took place on the ship's upper deck, with a long violet carpet trailing from the interior to the alter at the bow of the ship. Since the wedding was rushed, the ship was lined with very few decorations, save some wreaths, boquets, a cake, and silverwear to match.
Once the wedding was attacked by Scuttle and his legions of animals, the ship and its passengers were left in disarray. There were traces of water all over, and the banquet table was destroyed when the animals propelled Ursula onto the table.
What proceeded afterwards was Ursula revealing her true form and capturing Ariel before diving into the sea, and Eric leaving the ship in a lifeboat to pursue Ariel.
The ship isn't seen again until the end of the movie. It is used as the same ship to celebrate Ariel and Eric's wedding. Though little had changed about the decor, that time, the ship was used in the day time, and a new cake was made especially for Ariel and Eric.
The ship is then seen floating off into the distance under the rainbow made by King Triton, as Ariel and Eric share one more kiss.