When you're in dire need of more resources for an upcoming situation, eg. A night out that requires copious amounts of chemical stimulation.
Can also be used when you're in a situation where the females outnumber the males heavily.
Friend: Hey douche, we are going OUT tomorrow night and we are gonna hit it hard!
Me: We're gonna need a bigger boat.
Man look at the pussy up in this place! We're gonna need a bigger boat.