Climbing and Swimming

Climbing and swimming use movement but cost extra unless you have a dedicated speed.

• Movement cost: Each foot of climbing costs 2 feet of movement (effectively halving your speed while climbing).
• Climb speed: A creature with a climb speed uses that speed normally (1 foot per 1 foot of movement) when climbing, and has advantage on Strength (Athletics) checks to climb.
• Athletics checks: The DM may require a Strength (Athletics) check for particularly difficult climbs: slippery surfaces, sheer walls, climbing while taking damage. The DC depends on the surface:
• Knotted rope or ladder: No check needed
• Rough stone with handholds: DC 10
• Smooth stone: DC 15
• Wet or icy surface: DC 20+
• Falling: A failed Athletics check while climbing typically means the character falls and takes falling damage (1d6 per 10 feet).

• Movement cost: Each foot of swimming costs 2 feet of movement, the same as climbing.
• Swim speed: A creature with a swim speed uses that speed normally and has advantage on Strength (Athletics) checks to swim.
• Athletics checks: The DM may require Strength (Athletics) checks in rough water, strong currents, or stormy seas.
• Armor: Swimming in heavy armor is extremely difficult. The DM may impose disadvantage or higher DCs. Some DMs rule that characters in heavy armor sink without a swim speed.

Climbing and swimming through difficult terrain (e.g., climbing a surface covered in thorns, swimming through kelp) costs 3 feet of movement per foot — the normal double cost plus the difficult terrain extra cost.

See the Underwater Combat rules for additional restrictions on attacks and damage while submerged.