AI rendition based on witness descriptions, not an actual photo.
A scaled 'merman' said to have been caught in the Baltic Sea in 1531, from Johann Zahn's book of marvels · photo by Sean Linehan, NOS, NGS National Oceanic and Atmospheric Administration (NOAA) · Public domain (via Wikimedia Commons) · Image source
A sea creature of 16th-century lore said to resemble a bishop and to have been shown to the King of Poland.
FolkloreVerdict: We treat Bishop-fish as folklore: the record is stories and local reports, with no specimen or verified photo.