Currents and Flowing Water
Ocean currents, flowing rivers, and the like are difficult terrain or greater difficult terrain (depending on the speed of the water) when you’re swimming against them. At the end of your turn, the current moves you a certain amount of distance depending on its speed. For instance, a 10-foot current moves you 10 feet in the current’s direction at the end of your turn.
I don't see why someone swimming upstream should have their movement cut to half (or a third) in addition to being carried along by the current. Being difficult terrain should be a function of the water's turbulence, not its movement.
Swimming against a current is more tiring than calm water or swimming with a current. Turbulent (choppy) water mostly puts your head under water a lot, it's not that big a deal if you duck under waves and breath between.
If all the water in your vicinity is moving along smoothly at a steady rate, you have no way to even notice the current without looking around.
If all the water in your vicinity is moving along smoothly at a steady rate, you have no way to even notice the current without looking around.
I disagree from my beach/rip tide experiences growing up on the gulf coast. You know you're moving, it's only by looking at the shore that you realize how fast you're moving. And it's definitely more tiring to swim against than with the current.
And it's definitely more tiring to swim against than with the current.
I would guess that's mostly a psychological thing. If you're swimming against the current, you're going to swim for all you're worth, because that's the only way to make progress. If you're swimming with the current, you'll take it relatively easy because you're being helped along.