Bubbles

Kinda mixed mode really.
I would go into survival then type /gamemode 1 for creative. Find the nearest ocean and find random bubbles in it.

Step 1: Create new world. Use "Water Test 01" as the seed. Turn on cheats and starter chest. (game type survival)

Step 2: Type "/gamemode 1" as soon as you enter the game.

Step 3: Fly to the nearest ocean. X:51 Y:50 Z:217. There might be bubbles. If not just keep searching and look at the attachment for more information.

The bubbles are medium sized air pockets in the ocean.