Otomo Nin Surfermaru (Japanese: オトモ忍 サーファー丸) is one of the auxiliary "Otomo Nin" mecha from Shuriken Sentai Ninninger (2015). It is tied to the extra ranger Star Ninger (Kinji Takigawa) and is summoned via the Otomo Nin Shuriken: Surfer, first appearing around episode 17 (episodes 17–18, 24, 39–40, 42, plus the Ninninger vs. ToQger film). Its default mode is a purple submarine with a shark-like face, from which it rises into a humanoid "surfer" figure that rides a surfboard. Unlike some Ninninger mecha, it was not Japan-exclusive: it was adapted for Power Rangers Ninja Steel / Super Ninja Steel as the "Sub Surfer Zord," where it is assigned to the Gold Ranger.

Like the other Otomo Nin, Surfermaru functions as an interchangeable component of the main Megazord, Shurikenjin. In the Shurikenjin Surfer configuration it takes Shinobimaru's place to form the right hand/arm, while the enlarged Surfer Shuriken replaces the Shinobimaru head; the robot keeps the Drago Sword as a side weapon and gains a surfboard used to manipulate tidal waves. A notable point is that Surfermaru is the only one of the extra Otomo Nin with intended combination functionality with Bison King as well (Bison King Surfer).

The DX toy was made by Bandai Japan and released in June 2015 (official images revealed in May 2015) as a numbered entry in the Otomo Nin range (Series 03), retailing at 2,800 yen and including the accompanying Otomo Nin Shuriken: Surfer. The model is largely plastic (no significant die-cast), converts between submarine and surfer modes, and attaches to the DX Shurikenjin (or DX Bison King) via the Otomo Nin docking system. The Western release, the Sub Surfer Zord, was distributed under Bandai America for the Ninja Steel toyline.