Northern California received an unexpected visitor in its inland waters: a humpback whale spotted roughly 60 miles from the Pacific. The animal was first seen Tuesday moving through San Francisco Bay, then turned up Wednesday in the Sacramento River near the Rio Vista Bridge, witnesses told local media. One fisherman said he initially mistook the massive shape for a submarine and estimated it was about the length of at least half a school bus, ABC News reports.
Experts said the whale’s detour is unusual but not necessarily a sign of distress. The Marine Mammal Center reports the humpback appears to be in decent condition and is swimming on its own, though its presence far from the open ocean is considered out of the ordinary. The center said its cetacean team will assess and monitor the animal, per the AP. Identified via photo records as CRC-11620, the whale has been documented 15 times over 24 years between California and Mexico. Officials are asking boaters and onlookers to keep their distance, avoid steering it off course, and stay alert in busy waterways in case the whale surfaces unexpectedly.