The Doubleboat is a type of Blue that appears in the anime Blue Gender. Unlike other Blue variants which are insect or annelid-based, the Doubleboat does not belong to any recognised genus. It is one of the largest Blue types encountered by humanity and has a most peculiar body structure; specifically it appears to be two creatures conjoined at the tail.
The Doubleboat's body is covered in thick green skin and its shock-absorbent tissue protects it from impacts. Travelling on eight tree-trunk legs, it will attempt to crush Second Earth mechs with its sheer weight. A pair of thick, tubular antennae can be found atop each of the Doubleboat's heads that can spew globs of highly corrosive acid.
The Doubleboat's core is located within the connective area joining its two bodies. Since it is protected by layers of fat and muscle, the organ cannot be seen until the surrounding tissues have been breached. Bladed weapons are most effective for eliminating Doubleboats.