Inspired by mathematical structures found by theoretical physicists and by the desire to understand the 'monstrous moonshine' of the Monster group, Borcherds, Frenkel, Lepowsky, and Meurman introduced the definition of vertex operator algebra (VOA). An important part of the theory of VOAs concerns their modules and intertwining operators between modules. Feingold, Frenkel, and Ries defined a structure, called a vertex operator para-algebra (VOPA), where a VOA, its modules and their intertwining operators are unified.In this work, for each $n geq 1$, the author uses the bosonic construction (from a Weyl algebra) of four level $-1/2$ irreducible representations of the symplectic affine Kac-Moody Lie algebra $C_n^{(1)}$. They define intertwining operators so that the direct sum of the four modules forms a VOPA. This work includes the bosonic analog of the fermionic construction of a vertex operator superalgebra from the four level 1 irreducible modules of type $D_n^{(1)}$ given by Feingold, Frenkel, and Ries. While they get only a VOPA when $n = 4$ using classical triality, the techniques in this work apply to any $n geq 1$.