The water behind me is an ocean.
Not obsidian! Noooooo!
Also, I found out how you can mine cobblestone with just two buckets. One with water and the other with lava. Find a 5x5 hole, make a 2x high platform in the center. Place lava on top, let it fill the hole, take away the lava and switch to a bucket of water and place it where the lava was. The water will flow over the lava creating cobblestone. If you do it backwards, you get Obsidian.