[Gamer_Z]

I'm not familiar with the player anim indexes but what yo basically do:

pawn Код:

new Timer[MAX_PLAYERS];

public OnPlayerConnect(playerid)
{
    Timer[playerid] = SetTimerEx("CheckWater",5000,1,"i",playerid);
    return 1;
}

public OnPlayerDisconnect(playerid, reason)
{
    KillTimer(Timer[playerid]);
    return 1;
}

#define PLAYER_ANIMATION_SWIMMING (12345) // 12345 - here you need to fill in the ID of the swimming animation, I don't know what it is.
forward CheckWater(playerid);
public CheckWater(playerid)
{
    if(GetPlayerAnimationIndex(playerid) == PLAYER_ANIMATION_SWIMMING)
    {
        SetPlayerHealth(playerid,0.0);
    }
    return 1;
}

Enjoy and learn. :P

you can use the code on https://sampwiki.blast.hk/wiki/GetPlayerAnimationIndex , then go swim and check what the player animation swimming index is.