You might be interested in this:
Up until now it has been assumed that the special flow characteristics
exhibited by blood were mainly due to the presence of the red blood
cells, which account for about 45 percent of the blood's volume. Blood
plasma was generally regarded simply as a spectator that played no
active role. For decades, researchers have assumed that blood plasma
flows like water. After all, plasma, the liquid in which the blood
cells are suspended, consists to 92 percent of water. But results from
researchers at Saarland University and at the University of
Pennsylvania have now shown that plasma is a very special fluid that
plays a crucial part in determining how blood flows. The results
demonstrate that blood plasma is itself a non-Newtonian fluid.
As a non-Newtonian fluid, blood would certainly not behave like water.
The article is a fairly extensive study of the fluid dynamics of blood, but I think the critical part is that blood under high pressure (the bottom of the ocean) does not respond the way one would expect water to.
From the same article
Experts refer to these materials as "non-Newtonian fluids," of which
ketchup and blood are prime examples. These fluids have flow
properties that change depending on conditions, with some becoming
more viscous, while others become less viscous. Blood (like ketchup)
is a "shear thinning fluid" that becomes less viscous with increasing
pressure and it is this that allows blood to flow into the narrowest
of capillaries. The flow properties of water are, in contrast,
Think about an ocean full of ketchup.