Ship
A ship is a common mode of transportation in Dragon Quest games. The concept of giving the Hero's party a ship first appeared in Dragon Quest II and has appeared in all the subsequent games in the main series.
Possession
Gaining access to the use of a ship is typically the result of completing some sort of quest or objective. Normally, the point in the game when a ship is acquired is near the mid-point of the game, as having a ship allows access to areas already visited and new areas which are fundamental to the next portion of the game. In the case of both Dragon Quest II and Dragon Quest III, acquiring the ship is a segway to quest which requires the Hero to travel all over the world to retrieve specific items.
= Dragon Quest II
In Dragon Quest II, the ship is given to the Hero in the city of Lianport after saving the ship owner's daughter from a group of Gremlins.
Dragon Quest III
In Dragon Quest III, the ship is given to the Hero after bringing the king of Portoga some pepper.
Dragon Quest IV
In Dragon Quest IV, the Hero can use the ship after helping Taloon relight the sacred fire in the Lighthouse.
Usage
Traveling in the ship is much like traveling on land. Typically, the ship travels at the same rate of speed as travel by land. The party also will continue to encounter monsters while on the ship, although they will be aquatic rather than land monsters. The ship also follows the Hero whenever the Return spell or Wing of Wyvern is used. The ship relocates to the nearest body of water to the return point. This keeps the player from having to remember where the ship was last used.