Actually, it should be glued. Air is about 1000 times less dense than water. If it can leak one drop of water out, it can leak 1000 "drops" of air in. Secondly, the glue keeps it together. Friction will hold it for a while, but when it comes apart on you, it will be at the worst possible time.
Glue is cheap and it is easy to use.
Food for thought:
I've flooded nearly a hundred gallons of water onto the floor on several occasions. I'm not married, so forgiveness comes easy. For a 16yo, one gallon on the floor can end your hobby.