For example, this thing I whipped up in literally like ten seconds will kill someone when they are if the water. It probably doesn't work, but it is just an example.
PHP Code:
public CommandUse( id )
{
if(pev(id, pev_flags) & FL_INWATER)
{
user_kill( id )
}
else
{
// do nothing
}
return PLUGIN_HANDLED
}