Torches cannot be placed on the sides of blocks inside water if that water flows to the bottom of the world.

In creative, when you open up bedrock to expose the lower block placement limit (the bottom of the world), water that flows to (or is stationary over) this lower limit behaves strangely when torches are placed in it. It appears that you cannot place torches on the sides of blocks underwater when that water is directly above the bottom of the world. Remove the water and you can place torches on the sides of the blocks that extend into the bottom of the world just fine. Close off the bottom of the world (i.e. place a block at the lower placement limit and fill above with water, and you can place torches inside a column of water as expected.

Confirmed on Samsung Galaxy S6 (SM-G920W8), Android 5.1.1, MCPE 0.13.0.

Original report
When You Are On The Bedrock Level, You Cannot Put Torches When There is Water. Therefore, if you put torches on water it will place the torch and will quickly fall, But, in the bedrock level you cannot put it or nothing will happen if you try to put torches there again and again.