Here are a couple of example Maya files that show using Maya Fluids to handle ink in water. Generally speaking one simply creates a very high resolution fluid with "high detail solve" enabled, self shadowing on the fluid and very low transparency. The buoyancy should be negative instead of positive so that the ink flows down. The transparency should also be colored to partically match the fluid color, particularily if the background is light colored.
The second file was done in an attempt to help a user who had a seal bleeding as it swam. This was close to his reference, but real blood I'm guessing would be near black in this lighting condition.
oakBigLeaf.mel + oakBigLeaf.mel.icon