In its simplest form, AdS/CFT links the field theory on a stack of D3-branes to type IIB supergravity on $AdS_5 \times S^5$. When the theory on the branes is supersymmetric, it can admit marginal deformations that preserve supersymmetry. Understanding the supergravity solutions that are dual to the deformed theories is a generally difficult. I will begin by defining the 5d analogue of Calabi-Yau geometry for generic $D=5$, $N=1$ supergravity backgrounds with flux using the language of generalised geometry. I will then discuss how deformations of this geometric structure reproduce the marginal deformations of the dual field theories. Finally, I will comment on how this formalism might be used to recover the corresponding supergravity solutions.