NB! It seems this console command is not compatible with CS2.
Command Profile

SV_WATER_MOVESPEED_MULTIPLIER

CS:GO

This command sets how quickly you move in water compared to your normal movement speed.

Syntax
sv_water_movespeed_multiplier [Speed Multiplier]

Description

This command sets how quickly you move in water compared to your normal movement speed.

How To Use sv_water_movespeed_multiplier

  1. Enable the developer console in Counter-Strike settings.
  2. Open the console with the tilde key (~).
  3. Enter sv_water_movespeed_multiplier [Speed Multiplier], replacing bracketed arguments with the value you want, then press Enter.

This legacy command is not currently listed as compatible with Counter-Strike 2.

Syntax And Arguments

sv_water_movespeed_multiplier [Speed Multiplier]
Speed Multiplier What you want to multiply your default movement speed by to set your in-water movement speed. Use the number 0.5 to half your default movement speed when in water, or the number 2 to double it, for example. The default value for this command is 0.8.