...let it run 😅 .
Shots of streams, rivers, and waterfalls are tricky—light, reflections, creative choices, the whole deal. A lot of pros get really into that silky “silk effect” on waterfall water, and yeah, as a creative trick it looks cool. But for me, leaning realistic , I'd rather the water feel like that frantic rush we actually see in nature—when that's what's going on.
R10, RF-S18-150 at 24mm, ISO160, f/4, 1/15, long exposure to “slow down” the water and get a very slight silk effect.
Taste aside, for water photos in general it's worth having a polarizing filter (CPL)—it'll let you add, cut, or soften reflections that can mess with the shot. Overall, a CPL gets you pretty solid results. Only if you've got really fast lenses and you specifically want that “silk” look on moving water will you need longer exposures—and that's where an ND filter, which cuts light based on its strength, helps you get there.
This shot has two complementary parts: in the background, a small waterfall where this time I let the water “run” more so you could see how fast the current was moving, and up front that clear stream—super hard to catch in rivers—because it's laminar flow, looks like glass.
Here's an example of using a polarizing filter . By dialing it in, I could kill the reflections on the water surface and shoot the riverbed (that's the Manzanares River, by the way). On the left I intentionally left the reflection that covered the whole surface so you can see what the filter actually does.