void main()
{
    // ______________________________________________________________
    // Do a swimming check.
    // Note the 3.0 Players handbook P. 74 indicates a -1 penalty for every 5 pounds carried.
    // That seems a bit harsh in this environment.  Especially since I'm having to fake the
    // swim skill anyway.
    // Also note that the PHB indicates that the default ability is STR, but it seemed
    // appropriate to also include Dex and Con (endurance) since NWN doesn't provide the
    // swim skill at this point.
    // ______________________________________________________________

    object oPC = GetEnteringObject();
    if(GetIsPC(oPC))
    {
        int iDIFFICULTY = 18;
        int iSwimCheck = GetAbilityModifier(ABILITY_DEXTERITY, oPC) +
                         GetAbilityModifier(ABILITY_STRENGTH, oPC) +
                         GetAbilityModifier(ABILITY_CONSTITUTION, oPC) -
                         (GetWeight(oPC) / 250) +  // -1 for each 25 lbs carried
                         d20();

        if(iSwimCheck < iDIFFICULTY)
        {
            ApplyEffectToObject(DURATION_TYPE_TEMPORARY, EffectKnockdown(), oPC, 1.0f);
            ApplyEffectToObject(DURATION_TYPE_TEMPORARY, EffectDamage(d6()), oPC);
            SendMessageToPC(oPC, "You are choking on the water!");
        }

    }
}