The underwater robot Tommy Thompson engineered to explore the SS Central America had less power than an iPhone does today, but it was scientific genius in 1989.

The underwater robot Tommy Thompson engineered to explore the SS Central America had less power than an iPhone does today, but it was scientific genius in 1989. The remotely operated vehicle (ROV) Odyssey Marine Exploration used when they revisited the site this year is faster, stronger and more precise than the one that helped make history 25 years ago. "It's like comparing a lawnmower to a Chevy," says senior project manager Ernie Tapanes.

Nemo

Weighs 7 tons

25 horsepower

Nemo was powered electronically, and its control and data-logging systems were operated through five IBM XT personal computers. To move from one place to another, Nemo had to be lifted from the ocean floor and dragged by the boat.

Nemo could rotate in a full circle.

Nemo had two hydraulically powered robotic arms-one that was used to pick things up and another that moved the stereo-video camera, transmitted 3-D images to the surface in real time.

Nemo also had a camera for still photography. Photos were shot using Kodak Ektachrome film and developed in a darkroom on the boat.

Nemo could operate at a depth of up to 10,000 feet.

Zeus

Weighs 6.5 tons

150 horsepower

Two electric motors drive eight hydraulic thrusters-four for horizontal movement and four for vertical movement-easily and nimbly maneuvering ZEUS. Operators liken it to flying.

An advanced telemetry system allows operators to direct ZEUS to a precise location.

ZEUS has six cameras: one on either side and four up front, two of which are used for still photos and the others for HD video. Cameras can zoom in so close that operators are able to read the date on a coin.

HMI lights (like the ones typically used in the film industry) illuminate pitch-black wreck sites, allowing live video feed and still images to be transmitted to the surface.

Two hydraulic manipulators (arms) do all the work while ZEUS is submerged. They can extend up to 2 meters and mimic the controls of the operators at the surface.

ZEUS can operate at a depth of more than 8,200 feet.