Length approximately 3cm. This fish was extremely well camouflaged, it looked like a small piece of wood on the sandy bottom. It was very reluctant to swim and only made jerky movements when the dive guide came close with his pointer stick.
Specialized biologists have assured me that this is not a goby. More likely it is a phantom velvetfish (Paraploactis kagoshimensis). Velvetfishes (Aploactinidae) are a family belonging to the scorpionfish order (Scorpaeniformes). Field guides mention that scorpionfish evolved without a gas bladder which makes it always negatively buoyant. That explains why it did not seem able to swim: the poor thing just can't!