In this seed you spawn on an island. To the left of you there will be another island similar in size and looks but if you instead walk straight ahead and swim across the water you will reach a the coast of a mushroom island. The mushroom island is about the double size of the islands combined which you spawned on.
On the mushroom island there are many mooshrooms (mushroom cows) all over the island. The mooshrooms can be sheared for mushrooms which can be used to cook edible stew.