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

SV_DROWNING_DAMAGE_MAX

CS:GO

This console command sets the max amount of damage your player takes a second when drowning once the damage has scaled to it's highest level. This happens the longer you remain underwater.

Syntax
sv_drowning_damage_max [DPS]

Description

This console command sets the max amount of damage your player takes a second when drowning once the damage has scaled to it's highest level. This happens the longer you remain underwater.

Syntax And Arguments

sv_drowning_damage_max [DPS]
DPS The damage per second you take when drowning after you've been under the water for a while. The default value for this command is 5. Set it higher to take more damage from drowning, and lower to take less damage.