The media are having a field day with this.
Now let's break this one down.
1. The shooter, presumably firing from the Nisshin Maru, was in a concealed position when he fired that shot. Not one of the Sea Shepherd crew maintain they saw anyone with a rifle on board. So let's assume concealment as being out in the open would have given the shooter away.
2. Both the Nisshin Maru and the Sea Shepherd vessel were underway at the time and on moving seas. The shooter had to adjust not only for random waves and distance, but from a concealed position had to account for wind, also assuming that Watson was moving around as well at the time.
3. To make that one shot, and were not talking about a stationary book depository in Dallas, the odds are almost incalculable that the shooter got Waston directly over the heart with just one single round. It's a simply amazing shot.
Now for the real question, "why?"
Why would the Japanese government risk everything by trying to kill Captain Paul Watson?
They did use flash bang grenades and it was caught on tape, but the single shot?
Kevlar and Ballistic Vests
To penetrate a Kevlar or ballistic vest from a distance you need at least a 7.62 mm round. Obvious choices would be military rounds with some sort of armor piercing capability. That is assuming the shooter knew that Watson was wearing a bullet proof vest in the first place. Obviously from the penetration the shooter understood this, otherwise this kind of round would have passed through Watson and rattled around the ship.