Department of Conservation biodiversity ranger Jamie Quirk confirmed it was a southern right whale/tohora, and appeared to be about 8 to 10 metres long.
Tohora are a native migrant to New Zealand and are the only large baleen whales that can be seen from the beach.
Although Wainui Beach was the site of a mass stranding of 59 sperm whales on March 18, 1970, Quirk said baleen whales were less susceptible to strandings.
"Baleen whales don't tend to strand themselves. It is pretty common for them to get this close to the beach."
They tended to get one or two tohora off the Gisborne coast each year, Quirk said.
"It is pretty amazing to see it this close though. They are really spectacular, people travel all around the world to see this kind of thing and we have it on our back doorstep."
During the breeding season in winter and spring, they are mostly found in the waters around the subantarctic Auckland and Campbell Islands but there are occasional sightings around mainland New Zealand.