Just to expand on how to do this; you can just swap to your bucket of water and then hold down RMB to automatically place it when you reach terra firma. Obviously this isn't as automated as the OP was asking for but hey, it still works. If you really need it as automated as possible, you could even bind FastPlace and a macro for getting out your water bucket (there's tutorials on how to do that on the forums here if you don't know) to the same key to make it even easier.Its in fastplace on vape v3