Some important details from the Japanese ship owner and the crew who were witnesses to the attack
“The crew are saying it was hit with a flying object. They say something came flying towards them, then there was an explosion, then there was a hole in the vessel,” he told reporters. “Then some crew witnessed a second shot.”
Both attacks were witnessed by people on board. Both times they saw a flying object, discrediting the US first claim that it was a torpedo, and their second claim that it was a mine. The most convincing part is that they saw the second attack too. After the first attack, the crew would have been on alert looking for potential danger around them eg who launched the attack? Where did it come from? etc. The fact that they saw a flying object hit them while they were already on the lookout demonstrates they are likely to be accurate eyewitnesses.
“To put a bomb on the side is not something we are thinking,” he said. “If it’s between an explosion and a penetrating bullet, I have a feeling it is a penetrating bullet. If it was an explosion, there would be damage in different places, but this is just an assumption or a guess.”
On top of that, the damage on the ship is not consistent with the damage that would have occurred had it been a mine or explosion from outside. It was a penetrative attack, thus an artillery shell seems to be more likely. This is coming from the people who own and inspected the ship.
These inconsistencies explain why Japan (a very close and strong US ally) are asking for more evidence from the US. They are not convinced by the US’ story. They have access to the ship and the way it was damage. Their experts have looked over the damage and dont find it consistent with what the US is saying happened. They have access to the crew members who were first hand witnesses. Their stories do not corroborate with what the US is saying happened. All the US has said is that only Iran is capable of such a sophisticated attack, which is nonsense. The Japanese summarised it best themselves.
If having expertise sophisticated enough to conduct the attack could be a reason to conclude that the attacker was Iran, “That would apply to the United States and Israel as well,” said a source at the Japanese Foreign Ministry.