Instead customers will need to make a reservation ahead of time in order to secure themselves a unit. This was a similar situation with the iPhone during its launch where customers had to make reservation before they could go to the Apple store and buy the handset in person. So to secure yourself an Apple Watch, you will have to make a reservation via the online Product Reservation page, along with the specific model you were thinking about.
It seems that Apple is expecting that supply of the Apple Watch will be constrained at the start which is what we had heard earlier. The earlier report claims that Apple Watch retail stock is expected to be limited at launch and that customers who wish to purchase the device will either have to pre-order it, or like the document the folks at MacRumors obtained, will have to reserve it via the Product Reservation feature on Apple’s website.