PurposeThis　paper　aims　to　investigate　the　natural　vibration　frequencies　and　corresponding　vibration　modes　of　a　functionally　graded　(FG)　graphene-reinforced　composite　(GRC)　beam　with　geometric　imperfections　partially　submerged　in　fluid.　The　primary　objectives　are　to　analyze　the　effects　of　Sine　imperfections　and　varying　boundary　conditions　on　the　vibration　behavior.MethodsThe　study　employs　the　variable　separation　method　to　determine　the　fluid　velocity　potential　and　hydrodynamic　loading.　Circular　graphene　nanoplatelets　(GPLs)　are　utilized　to　reinforce　the　host　beam,　considering　both　uniformly　distributed　(UD)　and　FG　patterns.　The　effective　Young＇s　modulus　is　computed　using　the　3D　Halpin-Tsai　model,　while　the　Poisson　ratio　and　mass　density　are　determined　through　the　rule　of　mixture.　Governing　equations　are　derived　using　the　first-order　shear　deformation　theory　and　Hamilton＇s　principle.　The　solution　is　obtained　through　the　differential　quadrature　(DQ)　method　with　an　iterative　scheme.ResultsParametric　analyses　are　conducted　to　assess　the　impact　of　GPL　distribution　pattern,　fluid　depth,　and　end　supports　on　the　free　vibration　behavior　of　GRC　beam-fluid　interaction　systems.　The　findings　highlight　the　significant　influence　of　geometric　imperfections　on　both　the　vibration　frequency　and　mode　of　the　GRC　beam.ConclusionThis　study　underscores　the　importance　of　considering　geometrical　imperfections　in　the　analysis　of　GRC　beam-fluid　interaction　systems.　The　results　provide　valuable　insights　into　the　effects　of　varying　parameters　on　the　vibration　behavior,　emphasizing　the　need　for　a　comprehensive　understanding　of　the　dynamic　response　in　practical　applications.