barrel

Hi I'm in the process of building a 3x2M (10x6ft) boat on 6 220L containers. These containers have two holes, one has a threaded cap which should be completely watertight if tightened well using PTFE tape, but the other seems to have like a peel off type of cover. I'm wondering on the best way...

I guess maybe this is sort of off coarse but I just wanted to share an idea for a canoe I came up with about 18 years ago when I saw my son floating in the swimming pool in a barrel that had been cut in half. I originally used untreated wood ribs to hold it together but are now rotten so I am...