dnd: Underwater Combat

dnd_underwater_combat.md

Underwater Combat

Breathing

• Creatures can hold their breath for a number of rounds equal to their CON score before begining to drown
• A drowning creature can survive for CONMOD rounds and cannot take Actions or Reactions, after which they become unconsious and cannot be stabilized or regain hp until they can breathe

Movement

• Creatures without a natural swim speed must make "Swim" (Athletics|Strength) checks at the start of each turn (Calm water DC10, Flowing water DC15, White water/Rapids DC20)
  • Success means the creature can move at 1/2 their normal move speed
  • Failure means the creature can not willingly move this round, takes -DEXMOD to AC and has DISADV on Dex Checks and Saves until a successful swim check is made
  • Extreme failure results in an uncontrolled buoyancy movement (usually sinking) of 5ft per 5 under the Swim DC

Visibility

• The maximum perception range underwater is determined by the clarity of the water (eg Clear 100ft, Murky 30ft) and the depth (Dim light at [Clarity * 6]ft and Darkness at [Clarity * 10]ft)

Weapons and Attacks

• Weapons that deal Bludgeoning or Slashing damage have -2 to hit and do 1/2 damage
• Ranged weapons take a penalty of -2 to hit per 5 feet, and all listed missile ranges are halved
• Thrown weapons do not function underwater unless they are Darts, Javelins, Spears, Tridents or Nets

Spellcasting

• Casting a spell underwater that requires a Verbal component reduces breath by 1
• A creature holding their breath and concentrating on a spell must make a concentration check at the start of each turn with a starting DC of 10, increasing by 1 per turn spent concentrating underwater

Sources

• GM Tips 164 Underwater Campaign Considerations with environments effects swim and others
• Has anyone tried an underwater combat? What was it like?