Making an impenetrable mob room [Solution found]

Sorry, im dumb XD
Thanks also

 

Has anyone tried making a walling/flooring system with water sandwiched between 2 walls/floors? Much like designing Blast proof bases in factions.

Please excuse horrible txt example xD I haven't tried it in game, Yet​

 

It looks good but sadly it fails for the same reason 1 block high cavities fail, or alternating half slabs or even fences for that matter fail. /jump allows you to jump into and through blocks so the only way to stop it is to either make the command not possible in the first place(Portal magic which in vanilla can be used to name Villagers without trading - the more you know) or to completely fill the area when you leave so they jump through it all. The problem with the latter is if you have live stock or grass... it dies.

 

Dan, Wonder if we swap the water for lava would it work xD

 

Would prevent donors and whatnot, because it'd kill them but if you have fly or even god mode, you live.

 

But u can't die on other people island amyways haha.
Would prevent no one then