You shouldn't have a problem with security BUT, that's only if you travel either alone or with like 1 or 2 people. Groups are their targets and if your in the midst of a large group clearly of teenagers you'll get busted which is no big deal but it's a pain in the ass and embarassing.
Disclaimer: Underage drinking = bad....no claims to it
That said: Mariner is pretty strict when it comes to bringing anything onboard, especially alcohol and don't assume the guards are stupid, they know the water bottle trick so don't even waste your time, theirs or the alcohol's. Best bet is to purchase mini bottles that have ALL plastic on them and wear cargo pants and just walk on, no metal detector issues and they probably won't check because...teens aren't that smooth...or are we.