Monitoring of underwater pipelines through wireless sensor nodes (WSNs) is an important area of research especially for locations such as underground or underwater pipelines, where it is costly to replace batteries. In this study, a finite element sensitivity and comparative analysis for piezoelectric (PZT) energy harvester operating in a fluid flow is done to power underwater in-pipe WSNs. Two types of bluff bodies D and I-shaped are used for comparison. Finite element simulations results show that PZT energy harvester having I-shaped bluff body produces 2.24 mW, while energy harvester having D-shaped bluff body has the capacity to produce only 0.82 mW of power. I-shaped bluff body have significant impact on the performance of pipe and it introduces 6 times more head loss than D-shaped bluff body to maintain regular flow of pipe for the same fluid domain. It is concluded from the analysis that 12 PZT cantilevers in parallel arrangement are needed to maintain 4096 bits per second (bps) transmission of 512-Byte data packet once per 5 minutes with the piezoelectric harvester, using an integrated 7.1 J super capacitor that can fit into the bluff body together with the power electronics and acoustic transceiver.