The Seaick Brothers come from Tensou Sentai Goseiger (2010) and belong to the Seaick (sea) tribe, whose core-team member is Gosei Blue (Hyde). This entry is not a standalone main megazord but a set of several sea-creature Gosei Headers (ゴセイヘッダー) — the robotic animal heads that define the series, which act as auxiliary machines and dock with the larger Gosei Machines. In the US adaptation Power Rangers Megaforce (2013) they were carried over as the "Sea Brothers" Zords.

Goseiger's mecha gimmick is built around interchangeable heads: the Headers attach to the torso of Gosei Great (the Gosei Great Megazord in Megaforce) and replace its standard arm-heads, producing modified battle configurations with sea-based attacks; the Seaick Headers can also link to one another. The defining trait is therefore modularity — different mounted Headers yield different formations rather than one fixed super robot.

The DX toy was released in 2010 by Bandai (Japan) as "DX Seaick Brothers." Like the rest of the Goseiger line it is predominantly plastic with no significant die-cast content. Its appeal lies in the combination gimmick: the included Seaick Headers are compatible with the DX Gosei Great and can take the place of its arms and attachments. For the US market, Bandai America reissued the pieces alongside Power Rangers Megaforce as the "Sea Brothers Zords," but the Japanese DX release remains the namesake variant of this entry.