You can build ships in the next World of Warcraft: Warlords of Draenor update
Patch 6.2 for World of Warcraft: Warlords of Draenor will contain a new ship-building feature among other niceties.
Per the patch notes, shipyards can be constructed by characters which have a level three Garrison, and once the shipyard is formed, a ship can be built and set sail on missions.
Along with ship building, the Hellfire Citadel raid will be added in the new Tanaan Jungle zone - an area only accessible by sea, so you will need a ship obviously.
Hellfire Citadel conatins 13 deadly bosses including Kilrogg Deadeye, Gorefiend, a reanimated Mannoroth, and Archimonde.
A new dungeon difficulty, Mythic, is being added and it is geared towards players "enjoy tackling difficult content in smaller groups" and provides an alternate progression path.
Mythic Dungeons are on a weekly lockout, and drop gear that's item level 680 with a chance for boss at the end to drop loot that's item level 700. More information will be added as development continues.
The update is currently on the Public Test Realms but is without a release date.