This is a command which mimics Minecraft Beta's TNT mechanics: TNT can be activated by punching it, and lit TNT in water will deactivate and drop 1 TNT.
How to install
How to import this command into your world
First, you must give yourself a command block (If you are on a server, you must be 'OP'ed, and have access to /gamemode 1)
To get a command block, type
/give @p command_block in the chat.
Once you have a command block, right click it to open it's GUI.
Now, you must copy and paste the command from your browser into the game. Select the entire command from below, then right click and press 'copy'.
Next, go back to your minecraft world, and paste the command you just copied into the command block. There are a few different keys that may be used to do this, depending on your keyboard. The most common ones are 'CTRL + V', 'COMMAND + V', or 'STRG + V'
Finally, you can press done to exit the GUI, and execute the command block by powering it with a redstone block, a lever, or any thing you can get your grubby hands on. Just make sure you don't place it on top of the command block, or the machine will not be installed!
Show source commands
# This user did not upload the source commands!
summon falling_block ~ ~1 ~ {Block:stone,Time:1,Passengers:[{id:falling_block,Block:redstone_block,Time:1,Passengers:[{id:falling_block,Block:activator_rail,Time:1,Passengers:[{id:commandblock_minecart,Command:gamerule commandBlockOutput false},{id:commandblock_minecart,Command:fill ~2 ~-3 ~-1 ~7 ~-1 ~1 stained_hardened_clay 14 hollow},{id:commandblock_minecart,Command:fill ~2 ~-2 ~-1 ~7 ~-2 ~1 stained_glass 0 0 stained_hardened_clay},{id:commandblock_minecart,Command:scoreboard objectives add 42bttnt stat.useItem.minecraft.tnt},{id:commandblock_minecart,Command:setblock ~1 ~-3 ~ wall_sign 4 0 {Text1:"{\\\"text\\\":\\\"Made with\\\"}",Text2:"{\\\"text\\\":\\\"MrGarretto's\\\"}",Text3:"{\\\"text\\\":\\\"One Command\\\"}",Text4:"{\\\"text\\\":\\\"Combiner\\\"}"}},{id:commandblock_minecart,Command:setblock ~1 ~-2 ~ wall_sign 4 0 {Text1:"{\\\"text\\\":\\\"\\\",\\\"clickEvent\\\":{\\\"action\\\":\\\"run_command\\\",\\\"value\\\":\\\"scoreboard objectives remove 42bttnt\\\"}}",Text2:"{\\\"text\\\":\\\"\\\"}",Text3:"{\\\"text\\\":\\\"[Remove]\\\",\\\"color\\\":\\\"red\\\",\\\"bold\\\":true}",Text4:"{\\\"text\\\":\\\"\\\",\\\"clickEvent\\\":{\\\"action\\\":\\\"run_command\\\",\\\"value\\\":\\\"fill ~ ~-1 ~-1 ~6 ~1 ~1 air\\\"}}"}},{id:commandblock_minecart,Command:setblock ~1 ~-1 ~ wall_sign 4 0 {Text1:"{\\\"text\\\":\\\"BETA TNT\\\",\\\"color\\\":\\\"red\\\"}",Text2:"{\\\"text\\\":\\\"v1\\\",\\\"color\\\":\\\"dark_gray\\\",\\\"bold\\\":true}",Text3:"{\\\"text\\\":\\\"By mincerafter42\\\",\\\"color\\\":\\\"aqua\\\"}",Text4:"{\\\"text\\\":\\\"\\\",\\\"color\\\":\\\"dark_aqua\\\",\\\"bold\\\":true}"}},{id:commandblock_minecart,Command:summon armor_stand ~3 ~-2 ~ {CustomName:TogAct,Marker:1,NoGravity:1,Invisible:1}},{id:commandblock_minecart,Command:scoreboard objectives add 4vS8PY_A dummy},{id:commandblock_minecart,Command:setblock ~6 ~-2 ~ chain_command_block 5 0 {auto:1,Command:execute @e[type=tnt] ~ ~ ~ detect ~ ~ ~ flowing_water -1 tp @e[type=tnt,c=1] ~ ~-500 ~}},{id:commandblock_minecart,Command:setblock ~5 ~-2 ~ chain_command_block 5 0 {auto:1,Command:execute @e[type=tnt] ~ ~ ~ detect ~ ~ ~ flowing_water -1 summon item ~ ~ ~ {Item:{id:tnt,Count:1b}}}},{id:commandblock_minecart,Command:setblock ~4 ~-2 ~ chain_command_block 5 0 {auto:1,Command:scoreboard players set @a[score_42bttnt_min=1] tntplace 0}},{id:commandblock_minecart,Command:setblock ~3 ~-2 ~ repeating_command_block 5 0 {auto:1,Command:execute @a[score_42bttnt_min=1] ~ ~ ~ fill ~-5 ~-5 ~-5 ~5 ~5 ~5 tnt 1 replace tnt 0}},{id:commandblock_minecart,Command:setblock ~ ~ ~1 command_block 0 0 {Command:fill ~ ~-3 ~-1 ~ ~ ~ air}},{id:commandblock_minecart,Command:setblock ~ ~-1 ~1 redstone_block},{id:commandblock_minecart,Command:kill @e[type=commandblock_minecart,r=1]}]}]}]}