# Swimming *Source: Player's Handbook (2024) p. 376. Available in the Free Rules (2024)* While you're swimming, each foot of movement costs 1 extra foot (2 extra feet in [difficult terrain](3-Mechanics/CLI/rules/variant-rules/difficult-terrain-xphb.md)). You ignore this extra cost if you have a [Swim Speed](3-Mechanics/CLI/rules/variant-rules/swim-speed-xphb.md) and use it to swim. At the DM's option, moving any distance in rough water might require a successful DC 15 Strength ([Athletics](3-Mechanics/CLI/rules/skills.md#Athletics)) check.