Paintings Under the Sea
A 1923 New York Times Magazine article profiled Zarh Pritchard, an artist known for going underwater in a diving suit and painting what he saw once he resurfaced.
You might assume he did this because underwater photography hadn't been invented yet, but the first appreciable underwater photograph was taken in 1899. That year, Louis Boutan photographed Emil Racovitza holding a sign that read "Photographie sous-marine," French for "underwater photography."
However, the first underwater color photograph wouldn’t be taken until 1926, when National Geographic staff photographer Charles Martin took this photo of a hogfish off the Florida Keys.

So if you wanted underwater color images in 1923, Zarh Pritchard paintings were your best option. He explained his observational process to the Times journalist M.B. Levick:
Beneath the sea it is not all blue and green.
"You see yellows so bright you step back from them," says Mr. Pritchard; "vivid yellows, mustard yellows." He points to a picture of coral trees with yellow hills in the background, and tells how he had to retreat that the yellow might take its proper value. In the foreground of this picture are red fish.
"They're inquisitive," he continues. "They come and look at you. Little bits of paint float away from the tubes. They descend very gently, and you watch the little fish dart at them and gobble them — and wish they hadn't."
Paintings Under the Sea
Published: Sunday, August 5, 1923