If you are afraid your enclosure leaks, just go to Lowes and get a gallon of resin and a few bondo trowels.
Mix/pour the resin onto each wall of your enclosure and smooth it out w/ the trowels. Then, lean each corner up at a 45degr. angle and pour some resin there.
This whole process will take several hours, but cost no more than $40.
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EDIT:
If your enclosure leaks after taking these precautions....
A) Your sub is not sealing against the baffle...add weather stripping round the sub ID (or learn to cut the ID of a sub correctly)
B) Your baffle is flexing (add bracing to the baffle).
C) You can't build an even relatively squared enclosure for chit, and need to just pay a professional to build a proper enclosure for you.