Assuming there is no magic holding it aloft and it doesn't have the ability to hover, when a flying creature is knocked prone, it falls.

What happens if the creature was flying over a body of water? Can it effectively use its movement to "stand up" on its next turn and resume flying, or does it end up like that video of the bald eagle swimming, where its feathers are too wet and it can't reasonably get enough lift to take off again?

Ducks can take off from water, but I would argue that ducks have a swim speed.

  • 3
    \$\begingroup\$ Welcome to RPG.SE! Take the tour if you haven't already, and check out the help center for more guidance. Are you thinking of a particular creature? What is the creature's regular (walking) speed? \$\endgroup\$
    – V2Blast
    Commented Oct 23, 2020 at 5:45
  • \$\begingroup\$ Somewhat related: "Can you use the Fly spell to move underwater at a speed of 60 feet?" and "How does underwater rules work with flying familiars?" \$\endgroup\$ Commented Oct 23, 2020 at 6:08
  • \$\begingroup\$ The specific case where this came up was a Harpy affected by Sleet Storm \$\endgroup\$
    – Tantelope
    Commented Oct 23, 2020 at 13:02
  • 5
    \$\begingroup\$ I'm pretty sure that a harpy affected by sleet storm is kept aloft by the volume of curses ejecting from her mouth. \$\endgroup\$
    – nitsua60
    Commented Oct 23, 2020 at 15:45
  • 2
    \$\begingroup\$ @Tantelope In the future, please ask directly about the problem you're having. Trying to make it generic usually obscures important details, like the harpy's speeds or the existence of the sleet storm spell, and forces answers to spend some (or in the worst cases, all) of their time, energy, and screenspace on things that don't answer your question. \$\endgroup\$ Commented Oct 23, 2020 at 19:08

1 Answer 1


RAW: The flier can escape the surface.

Depending on our flier's normal and flying speeds and the condition of the water (normal or difficult terrain), she'll be able to escape just fine, it's only a question of how long it takes to get out of being prone.

If she's lucky, she'll fall, land, and not be prone because she took no damage from the fall, whether by falling less than 10 feet, monk slow fall, having cat's grace, etc. In this case, she can immediately spend her whole movement as her flying speed dictates.

If she's less lucky, she'll fall and land prone. She doesn't have a swim speed, so she needs to fall back on walking speed at +1x cost. 'Standing up' from prone in this instance costs her entire walking speed. If she has more flying speed than she does walking speed, she can then spend the difference flying.

If she's least lucky (such as with your harpy and her worst day ever), she'll fall and land prone in difficult waters, where the movement cost is bumped up to +2x. Now, 'standing up' costs her whole walking speed and a half. But she can use the Dash action, leaving her with half her walking speed to spare. She can still get to flying immediately only if double her flying speed exceeds the 1.5x walking movement she spent on standing up.

All the relevant rules are in the Player's Handbook, pgs. 182-191.

Your harpy's worst day ever is only one round long.

For your harpy (speed 20 ft, fly 40 ft, MM p. 181) in sleet storm (20 ft tall, 40 ft radius cylinder, area forces Dex save or go prone and is difficult terrain, PHB p. 276), it's even money whether she falls prone due to the spell being only twice as high as the threshold for not taking falling damage, but at the beginning of her turn the spell might knock her prone again at the beginning of her turn anyway.

Assuming it does, the difficult terrain forces her to spend 30 feet of movement to stand up, which she has if she Dashes, leaving her with 80 feet of flying movement minus the 30 she spent on getting up.

50 feet of flying movement, even if you rule that the airspace is also difficult terrain (the spell only specifies the ground), is enough to leave the sleet storm through the top (and from the sides unless you're within 15 feet of the epicenter).

"But what about..."

You'll notice that none of this addresses any of your concerns about wet wings or being too slow to take off. That's because D&D isn't a physics simulator. This is just what the rules as written directly say about your flier's ability to get out of a water landing, and are not (and will never be) able to address every edge case. The space between is up to your DM.

The rules do suggest that a DM may ask for a Strength (Athletics) check in order to make any headway against rough waters, and per Rule Zero a DM could certainly apply the concerns you've listed to nullify a creature's ability to fly under certain conditions. Yet they could also reject it for game balance purposes. It's all up to them and how they want to run their game.

  • \$\begingroup\$ Exactly. +1. Not everything that flies has wings. \$\endgroup\$ Commented Oct 23, 2020 at 14:50
  • \$\begingroup\$ Is it reasonable to interpret the surface of the water as being the "ground" for the purposes of determining difficult terrain? \$\endgroup\$
    – Tantelope
    Commented Oct 23, 2020 at 19:24
  • \$\begingroup\$ While I would suspect the answer is "it's one of those edge cases that's up to your DM", that is a good question to ask, I encourage you to post it as a question instead of a comment. It's not unusual at all for questions to beget questions like this, often with links to the previous question. \$\endgroup\$ Commented Oct 23, 2020 at 21:51
  • \$\begingroup\$ What if she sinks? \$\endgroup\$
    – Ben Barden
    Commented Oct 23, 2020 at 23:49
  • 1
    \$\begingroup\$ @BenBarden D&D is not a physics simulator. \$\endgroup\$ Commented Oct 24, 2020 at 1:39

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