"Pre-industrial" sailors didn't drink "so much" while out at sea. They mostly drank water, and alcohol was a perquisite and sometimes a reward. I've written about this before:

https://www.reddit.com/r/AskHistorians/comments/2aos9q/how_large_were_the_daily_rations_of_alcohol_in/

and

https://www.reddit.com/r/AskHistorians/comments/3amzc3/i_keep_reading_about_the_large_amounts_of_alcohol/