[The following is in reference to conditions upon merchant vessels in the 17th century.]
The captain of one Danish East Indiaman was so maddened by the plague of scuttling vermin on board his ship that he offered his sailors a tot of brandy for every thousand cockroaches they killed. Within days, the crushed bodies of 38,250 insects had been presented for his inspection.
Source:
Dash, Mike. “The Tavern of the Ocean.” Batavia's Graveyard. Three Rivers Press, 2003. 105. Print.
There probably wasn't all that much to do on those ships in the 17th century, so killing bugs with a hope of getting drunk would probably be the highlight of a trip.
Also imagine living with that many roaches on a ship out at sea. Your bed would have roaches, the cargo you'd be delivering would be infested...ugh