Phil Thompson was walking along a jetty at the Bellarine Peninsula in Victoria, Australia, when he spotted a rainbow reflecting off the sea to create two visible arcs of colour emanating from the same spot.In the traditional double rainbow, the two arc would have he same radius of curvature. The reflection phenomenon is explained at Wikipedia:
Where sunlight reflects off a body of water before reaching the raindrops (see diagram), it may produce a reflection rainbow (see photo at the right), if the water body is large, quiet over its entire surface, and close to the rain curtain. The reflection rainbow appears above the horizon. It intersects the normal rainbow at the horizon, and its arc reaches higher in the sky, with its centre as high above the horizon as the normal rainbow's centre is below it. Due to the combination of requirements, a reflection rainbow is rarely visible.
Six (or even eight) bows may be distinguished if the reflection of the reflection bow, and the secondary bow with its reflections happen to appear simultaneously [example below, from Norway, posted at APOD]:
Top photo: Phil Thompson / SWNS.com, via The Telegraph. Lower photo: Terje O. Nordvik.