Said of beer (or other adult beverages) that either have low alcohol content or is relatively tasteless, because it's fucking close to water.
The humor, of course, comes from a cognitive shock. One might expect the phrase to be a metaphor for something beautiful, what with the associations of «making love» as an intimate act; and with a canoe evoking idyllic imagery of peaceful lakes and gentle rocking.
In my experience, it could/should also be said of drinking (beer) on the beach. All my life I've lived on relatively high altitude (over 2,000 meters) and I'm not really a beach person, so I don't visit it often. But the last three times that I've been at sea level I could never get even a slight buzz despite the volumes consumed (well over a gallon).
Many of my friends and acquaintances have experienced this as well, but I have yet to find conclusive evidence on why this is the case. My own hypo-hypothesis is that living in higher altitudes might have something to do with it.
I only have a lot of anecdotal evidence, so I don't know whether «getting drunk is harder at sea level» is truth, selection bias (since most people I've asked have also lived for extended periods at high altitudes), pure luck—something that might have nothing to do with the perceived variable—or even a weird coincidence.
The most often proposed hypothesis is that «you sweat more at sea level» but I'm not really convinced—after all there are drunks at sea level. First, because on none of the aforementioned occasions there was a particularly hot weather. Second, because most times when this comes up, inebriation kicks in before serious scientific discourse.
Goldfish ← Andy’s Brevity Quest 2019 (283 words) → Galaxy Song