It depends on which fluid and what you intend to do with the properties. As we know practically nothing about astrophysical fluids, this must be quite speculative. I started a project with a colleague on extremely high pressure water, but never finished. I have some Russian data for water at very high pressures. The IAPWS-SF95 doesn't cover such elevated pressures, so a new formulation would be required. I could finish that work if you're interested in water.

Thanks, Dr. Benton. I am interested in developing stability theory of diversified astrophysical plasma fluids.

Your water-work may please be shared with me. I am optimistic on your works, your projects.

Dear Dr. Benton, thanks. The water work still lying pending with you, may now reach to the goal, if positively cooperated in full faith.