Cruises and underage drinking - help me out /r/travel!

Hey r/travel, a couple of friends and I are planning on going on a cruise in June to any destination. The deal breaker is being able to drink alcohol under the age of 21. Our ages are 22, 20, 20, and 19. Not sure how this subreddit feels about under age drinking, but I promise that we are all responsible and know our limits. What advice does r/travel have for me and my friends? Suggest destinations, tips, and cruise lines. Conversation is encouraged! Hope this is the right subreddit.