Does an ocean or sea count as Running Water against a vampire?

Question

The vampire stat block states (Monster Manual, p.297):

Vampire Weaknesses.
The vampire has the following flaws:
[...]
Harmed by Running Water. The vampire takes 20 acid damage if it ends its turn in running water.

If I were to run a nautically themed Curse of Strahd campaign, could the players simply knock Strahd into the ocean to make this weakness take effect, or, is the only running water like a river that has an effect on the vampire?

My thought is that a stream or river's water moves continuously in roughly one direction and roughly constant speed (excluding some seasonal outliers), whereas an ocean's movement is subject to tides and waves, so the movement is not consistent in a direction, and may not be considered 'running' because of this movement.

Currents in an ocean do tend to move in one direction, but for something the size of a humanoid the wake of a boat, the wind blowing, and creatures moving below the surface are more likely to affect the water around the creature, thus not putting the creature in 'running' water, just moving water, which seems to not count as 'running'.

If the ocean can be considered running water, would the doldrums be considered standing water?
While the ocean as a whole is moving, this one particular area is stationary, is that enough to remove the 'running' tag to this water?

Answer 1

It's ambiguous

Typically, oceans and lakes are not considered running water, which refers specifically to rivers and streams, so you should feel free to make whichever rulings make the most sense for the game you want to run.

But honestly, feel free to bend or replace the Monster Manual write-up to do what you want to do. Real-life vampire lore is broad, varied, and often self-contradictory (because there isn't actually one single body of 'vampire lore', but a large complex of local stories and beliefs that don't take into account what the next county over might think). You have all the justification you need to make up rules about how your vampire captain is going to work. As long as the rules are consistent in your adventure, you should be fine. Any complaints ought to be easily quashed with a simple "These are a different kind of vampire with different weaknesses", if necessary.

Dracula

As an example of a vampire with different weaknesses than D&D uses, a great deal of what people think of today as vampire lore is based on Bram Stoker's Dracula -- which, realistically, was Stoker picking and choosing a handful of elements from different vampire myths and mashing them together into something more-or-less coherent.

In the story, there's no special effect of running water specifically; Dracula is unable to cross bodies of water under his own power. He must be transported across the sea in the hold of the Demeter. He's able to come out of his coffin to murder the crew, so long as he remains on deck, but is apparently unable to cross over the ocean's surface. Once the ship arrives in England, he does not leave the ship until it runs aground, at which point he immediately leaps onto the beach (in wolf-form) and flees the area. It's notable that he didn't simply go into bat-form (which he uses elsewhere in the novel) and fly to the shore as soon as he was within the harbor. Instead, he remained on the ship until it actually made contact with dry land.

You should feel free to use this lore or ignore it to whatever degree you like.

Answer 2

The DM decides.

When we’re talking about definitions of words that aren’t game terms, the DM has to make a ruling. “Running water” is not a game term with a game-specific definition in the rules, so the DM decides.

For your specific game, think about what makes the most sense for your adventure’s main villain. Is he the vampire Lord of the Sea? Then it probably doesn’t bother him that much.

Answer 3

"Running water" in this context typically refers to waters with a current.

The more modern version of "running water" that we tend to think of is "running water from the tap," which still makes 'running water' a synonym for 'flowing water'.

Oceans, streams, rivers, tributaries, etc. all have a current and a/multiple direction(s) of flow.

An isolated, man-made lake with no connecting bodies of water, or a still canal, like a filled tub of water, would be an example of water that does not count as running.

Running Water isn't a game term, but with Plain English being the default rule of 5e, this 'reading' removes most dilemmas around the rule, at least until someone throws a vampire in a full bathtub under a running tap, or a horse trough under a water pump.

<I'd probably give the player inspiration for trying a funny and let them know it unfortunately doesn't work in that case.>

So what about an ocean, and in particular a doldrum?

An ocean has currents and water flows into it from multiple sources called estuaries, so for the purposes of this scenario it should count.

Doldrums refer to regions of water near the equator that are windless, where sailing ships get stuck. While this reduces wave chop, that has no impact on the flow of the currents in the water itself.