Sperm whales weren't the only thing we saw in Ogasawara.
We came across two species of dolphins (Tursiops aduncus and Stenella attenuata), as well as a family of Cuvier's beaked whales (Ziphius cavirostris...I came oh so very tantalisingly close to getting in-water photos of them!).
We also rescued a baby Bulwer's petrel (Bulweria bulwerii) that might have left the safety of its nest too soon. It was adrift in the water, unable to fly. Three of us managed to surround it, allowing me to grab hold of the frightened bird and take it back to land to be nursed to health and set free a few days later.
The most adrenaline-inducing non-sperm whale encounters, however, were with two large marlins that buzzed us at close quarters on two separate occasions...both times while we were preoccupied with large cetaceans.
This one was probably around two to two-and-a-half metres long (without the pointy part):
One of the marlins that buzzed us during a whale encounter
I've gone for years without ever seeing a marlin in the water, and now I've seen three in the past three months: one in Tonga, and two in Ogasawara.
By the way, does anyone know what kind of marlin this is? The local fishermen suggested that the fish were either striped or blue marlins.