The Nikonos was intended for underwater or all-weather work, it was water pressure-resistant to depths up to 50 m. The Nikonos was a development of the Calypso introduced in 1961 by Spirotechnique, Nikon acquired production and sales rights to the Calypso in 1962.

Two standard lenses were available - f2.5 35 mm W Nikkor and f3.5 28 mm U-W Nikkor. The U-W lens was for use only underwater and had a biconvex front glass to correct distortion and chromatic aberration in water, the 35 mm lens had a flat front glass.

The two knobs on the lens are for focusing and aperture control, as the aperture is altered the depth-of-field is shown against the focusing scale. The aperture scale is non-uniform.

Accessories included a flash gun, frame finder and close-up kit. The price was £106/15/8. The Nikonos II was introduced in 1968.