The Poseidon appears to be a torpedo-shaped robotic mini-submarine which can travel at speeds of 185 km/h (100 kn). More recent information suggests a top speed of 100 km/h (54 kn), with a range of 10,000 km (5,400 nmi; 6,200 mi) and a depth maximum of 1,000 m (3,300 ft).

Typical depth of the drone may be about 50–100 meters for increased stealth features in low-speed stealth mode. Low depth in stealth mode is preferred because sound waves move to ocean floor and reduce radius of detection. Submarines use the same strategy in silent running mode.

It is 1.6–2 meters in diameter and 24 meters long. The warhead shown in the leaked figure is a cylinder 1.5 meters in diameter by 4 meters in length, giving a volume of 7 cubic meters. Comparing this to the volumes of other large thermonuclear bombs, the 1961 Soviet-era Tsar Bomba itself measured 8 meters long by 2.1 meters in diameter, indicating that the yield is at least several tens of megatons, generally consistent with early reports of 100 megatons. Some reports suggest the yield of the Poseidon's warhead is as low as 2 Mt.