Rys, I am a cannon maker and making cannons is quite easy

!
1 = block
2 = TNT (Gets flooded with Water when activated)
3 = (Place bucket of water at)
4 = AIM AREA (place TNT to shoot at)
5 = Red Dust on a block
6 = Pressaure Pad
4
12556
125
125
125
135
1
Thats a simple cannon (put water bucket at the end facing the direction you want to fire).
Put TNT on all 2s and a TNT at the 4. Red Dust goes on the 5s (hooking to the tnt in the water). When activated wait a sec then smack the TNT on the 4. So when the TNT explodes in the water (No damage to cannon or floor due to water) the tnt on the 4 will fly and explode somewhere