The Whale Probe is the non-living main antagonist in Star Trek IV: The Voyage Home. It was the designation for a probe of unknown origin, which visited Earth in 2286. Dwarfing a Federation Miranda-class starship and Earth's Spacedock, the Whale Probe was cylindrical in shape, and carried a small sphere at the front, physically detached from the Probe, but connected by an energy beam. The sphere's purpose was as a communication device, amplifying the Probe's broadcast of its calls to enormous levels, impacting on power systems and ecospheres.
In comparison with the Earth Spacedock it passed by at rather close range, the Whale Probe's estimated length was in the vicinity of 70 kilometers – one of the largest space vessels ever encountered by Starfleet. First Contact with the probe by a Federation starship was made by the USS Saratoga while patrolling the Neutral Zone. The Saratoga was disabled by the probe's powerful communication, as were at least seven other vessels along the probe's route to Earth, including the starships USS Yorktown and USS Shepard, and two Klingon vessels. USS Saratoga's scan analysisAfter disabling Earth Spacedock and the prototype USS Excelsior, the Probe settled over the planet, directing its communications attempts towards its oceans. When it received no response, the Probe began vaporizing Earth's oceans, creating an impenetrable cloud cover over the planet, causing surface temperatures to plummet rapidly.
The Federation President was forced to send out a planetary distress signal, which was picked up by Admiral Kirk, aboard the "HMS Bounty", a captured Klingon Bird-of-Prey. Spock, also on board, quickly established that the probe's call was intended for the extinct cetacean species of humpback whale; Spock theorized that some other species had once been in contact with whales, and had sent the probe after the species went extinct to find out why they had lost contact.Since destroying the probe wasn't possible, and they would be unable to communicate with the probe itself due to their ignorance of the whale "language" even if they could duplicate the sounds, Kirk determined that the only way to stop the probe was to find some humpbacks who could answer it.
Consequently, the Bounty was taken into the past via the slingshot effect, and successfully retrieved two of the species from 1986. Returning to Earth, the two whales were able to respond to the probe's call, and it departed for an unknown destination, restoring power to the vessels it disabled along the way.
The whale probe indeed had caused a lot of damages to a lot of ships and even Earth, but the true main antagonist of Star Trek IV was 20th Century Humans. Humans hunted the Humpback Whale until the species extinction which prompted the unknown aliens to construct and send the probe to Earth to figure out why they lost contact with the whales.