Way back in 1994, engineers at MIT unveiled Robotuna. Inspired by the 160 million-year-old species, the aptly named, four-foot-long submersible robot required over 2,800 components, including 40 ribs, tendons, a vertebrae-like backbone, and even a Lycra covering to mimic the fish’s skin. Now, nearly two decades later, yet another MIT research team (including one Robotuna veteran) have unveiled their new underwater successor to the breakthrough fishbot—a modular creation composed of simplified, repeating structures instead of individualized pieces that can resemble everything from an eel to a hydrofoil wing.

Their findings, published recently in the journal Soft Robotics, showcase MIT’s new advances in developing deformable, dynamically changing underwater robotic structures. This ability is key for submersible robots, since it allows them to move through water much more efficiently, as countless varieties of fish do in rivers, lakes, and the open ocean.

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The team’s new design relies on lattice-like pieces called voxels, which are stiff in structure yet still low-density, and allow for large scalability potentials. The voxels are made to be load-bearing in one direction, yet soft in others through a combination of various materials and proportions, including cast plastic pieces. The entire design was then encased in a rib-like support material, and all of that was covered in waterproof neoprene.

To demonstrate these advances, the team created a meter-long, eel-like robot composed of four structures, each made of five voxels. An actuator wire attached to each end’s voxel allows the robot to undulate accordingly, causing the snakebot to move through water. Unlike the two-year construction time for its Robotuna ancestor, however, the new robot only took two days to build.

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“There have been many snake-like robots before, but they’re generally made of bespoke components, as opposed to these simple building blocks that are scalable,” Neil Gershenfeld, an MIT professor and research team member, said in a news release.

Aside from scalability, the voxels allow for numerous other design potentials, including a winglike hydrofoil also built by the team. Resembling a sail, the second construction shows promise for integration onto shipping vessel hulls, whether they could generate drag-inducing eddies to improve energy efficiency. There’s also talk of a “whale-like submersible craft” capable of creating its own propulsion. Given the voxels’ drastically shorter build times, however, that prototype could be here before we know it.