Beta 1.5

From http://www.minecraftwiki.net/wiki/Fish; http://www.minecraftwiki.net/wiki/Dragons; http://www.minecraftwiki.net/wiki/Whales;

Fish are a planned passive mob. In the Halloween update, Notch said he would add fish. However, he had limited time, and was thus only able to add them as an item. There is coding for fish in the game, but no model currently exists.

Dragons are a planned mob. Notch hinted during the Spider Jockey skeleton update that he will add Dragons to the game. Dragons may also be able to fly or breathe fire. Notch confirmed in his Twitter that he will definitely add a form of flying transportation. There is a chance that Dragons may be able to be ridden in a similar manner to pigs, which would indicate that Dragons are passive or may need to be tamed before being ridden.

Whales have recently been confirmed as a sea mob, although their purpose hasn't been specified, they could be a source of oil for lamps or possibly even a new source of energy. However, the squid has been the update for Beta 1.2, as the first try of whales was right before Beta 1.2, Beta 1.1_02.