Notch should put sponges for survival mode. They can be found underwater in groups of 2 - 5. The sponges
will produce bubbles if exposed to water. To obtain sponges you could use your hand or a shovel for fast digging.
They can rarley spawn in underground water lakes. If you put sponge next to lava, it will catch on fire.
Also the bubbles that are being made can be used to go up water faster. Stand on a sponge and you
could blast off.