This is swimmer.
In the calligraphy class I attended when I was little, at the occasion of first writing of the year, we used to make ink by rubbing solid inkstick on the inkstone instead of using commercially available ink.
It is often watery even after rubbing it many times, and I remember having a hard time because it did not have the ideal concentration and stickiness.
Every year when New Year time comes, I feel grateful for the convenience of the ink that can be used immediately after pouring it from the container into the inkstone.
The ink was patented in Japan in 1893.