Blanks for forming clamshell containers and the resulting clamshell containers are described. The clamshell containers include a tray and a lid that are hingedly connected together. The tray is liquid tight, and typically includes gussets on each corner to prevent leakage. The lid and tray can be locked via at least one locking mechanism, optionally two different locking mechanisms. A first locking mechanism involves a front panel on the tray, with an extension portion that terminates in a hook or tab. The extension portion can fold over the front panel of the lid, and the hook or tabs slide into a slit(s) on the top of the lid. An optional second locking mechanism involves lid detents and tray detents. In some embodiments, in the locked position, the lid detents are underneath the tray detents and the tray detents retain the lid detents in place until a force is applied.