I made one order at scuba.com with 5 items. A week later, with no email about my order status, I checked the order status online. It said, "Order Is Being Pulled For Shipping." So I emailed support. They simply said one of the items is out of stock and is expected to be restocked in 2 or 3 weeks.
You can still order that item and pay for it, and you won't know it's not in stock unless you contact support. You won't get an email alerting you about it. They won't offer to ship the rest of your order separately. This is an unpleasant experience.