The term 'watery part of blood' refers to the components of blood that are liquid. These components include SERUM (5 letters), PLASMA (6 letters), and sera (4 letters). SERUM is the clear, yellowish liquid that separates from the blood when it is allowed to clot. PLASMA is the straw-colored liquid component of blood that contains proteins, salts, and other substances. Sera is a type of SERUM that has been treated with an anticoagulant to prevent clotting. All three of these components are essential for proper functioning of the body.