[Feature] Drowning in the pool

[mbc]

added this, thanks! Just to note, I moved your code a bit because it was placed in between an already-existing if/elseif. 

Also removed some unnecessary returns. for example here, a return..() does nothing because there's no parent proc to call: 

Code:

if (istype(src.shoes, /obj/item/clothing/shoes/flippers)) //you dont drown if you have flippers
    return..()