The modern legend of the Loch Ness Monster is born when a sighting makes
local news on May 2, 1933. The newspaper Inverness Courier relates an
account of a local couple who claim to have seen “an enormous animal
rolling and plunging on the surface.” The story of the “monster” (a moniker
chosen by the Courier editor) becomes a media phenomenon, with London newspapers sending correspondents to Scotland and a circus offering a
20,000 pound sterling reward for capture of the beast.

After the April 1933 sighting was reported in the newspaper on May 2,
interest steadily grew, especially after another couple claimed to have
seen the animal on land.

Amateur investigators have for decades kept an almost constant vigil,
and in the 1960s several British universities launched sonar expeditions
to the lake. Nothing conclusive was found, but in each expedition the
sonar operators detected some type of large, moving underwater
objects.

A plesiosaur and mosasaur.  An illustration from a 1908 "Outing
magazine" article.