Ever since the 1.8.2 update was pushed through until the current version which is 1.8.6, the player no longer can be launched by TNT as compared to the versions 1.8.1 and below. The 1.8.2 patch was supposedly intended to fix the TNT cannon nerf. It has accomplished its task of fixing this TNT cannon nerfing, but along with it was the total elimination of TNT player launchers. Players no longer can be launched by TNT, even without watering the TNT; placing it in water then priming it. However players still do get launched by exploding creepers and exploding beds in the nether. I do not know if this was an intended feature/fix along with the 1.8.2 patch that fixed TNT cannons or just a bug. Attached is the image of the TNT player launcher used. Note that there is an infinite water source below the TNT so that when the primed TNT falls down into the water it will stay at the same place.