Hi, I am a owner of a PVP server and we have the problem that Water and Lava protects any block behind it, as this is normal in Minecraft.. However we have a plugin called "Obsidian Destroyer" This plugin allows you able to destroy Obsidian after a certain amount of hits, with TNT. It also allows you to destroy Obsidian that is covered in water / lava. This ability to destroy Obsidian behind water / lava only appeared after Minecraft 1.0 / Bukkit 1.0 / Bukkitdev 1400+- came out. In Minecraft 1.8 you were not able to destroy Obsidan behind water / lava using this plugin. What I'm trying to say is, that maybe this plugin has found some way around the whole process of protecting blocks behind water / lava! And if someone could look into this, and apply it to other blocks aswell, that would just be fantastic. However every other block behind water / lava, is undestroyable, as described at the top. I am offering a developer 50 EURO to come up with a plugin which removes the ability of water / lava to protect blocks from TNT. All of the above also includes Creeper explosions. Each type of block should have a damage value, and should be able to remember the damage applied to it, this is active in the Obsidian Destroyer plugin for obsidian only! I don't know why Notch has invented the water / lava resistence thing, the only reason I can find is the TNT cannons, which are important to stay working.
I can do this for you if you give me a bit more detail...what I am getting is you want tnt to blow up blocks while in water or lava?