We've all duck hunted in submerged pit blinds... but are they legal?

Take a look at what i've highlighted below... What's the difference in a pitblind and sinkbox?

WHAT HUNTING METHODS ARE ILLEGAL?

No persons shall take migratory game birds:

• With a trap, snare, net, rifle, pistol, swivel gun, shotgun larger than 10 gauge, punt
gun, battery gun, machine gun, fish hook, poison, drug, explosive, or stupefying
substance;

• With a shotgun of any description capable of holding more than three shells, unless
it is plugged with a one-piece filler, incapable of removal without disassembling the gun, so its total capacity does not exceed three shells. This restriction does not apply during dates States haves selected under the Conservation Order for light geese (i.e. greater and lesser snow and Ross’s geese) or those selected for the control of resident Canada geese.

• From or by means, aid, or use of a sinkbox or any other type of low floating device, having a depression affording the hunter a means of concealment beneath the surface of the water;

• From or by means, aid, or use of any motor vehicle, motor-driven land conveyance, or aircraft of any kind, except that paraplegics and persons missing one or both legs may take from any stationary motor vehicle or stationary motor-driven land convey- ance;