AI rendition based on witness descriptions, not an actual photo.
Drawing of the sea creature that U-28's commander, Georg-Günther von Forstner, said he saw in 1915 · Rupert T. Gould and Georg-Günther Freiherr von Forstner · Public domain (via Wikimedia Commons) · Image source
A marine reptile allegedly seen by U-28's crew in 1915.
OpenVerdict: U-28 creature remains unconfirmed: the record is reports, with no specimen or verifiable photo.