With the growing activities of diverse Maritime Internet of Things (MIoT), mobile edge computing (MEC) becomes a promising paradigm to provision computation and storage for computation-intensive tasks of marine users. Although the edge server (ES) deployment and service placement are important issues in the field of MEC, research on joint placement is often overlooked, particularly in the MIoT. In this paper, we propose the buoy-based ES deployment and service placement (BESDSP) problem for MIoT networks, aiming at maximizing the total profit while considering the location constraints of buoys, the different service request rates, the income and delay cost of service provided by ESs, as well as the characteristics of maritime channels. Then, we propose a heuristic approach, the genetic-BESDSP (G-BESDSP) algorithm, to solve the BESDSP problem. Simulation results demonstrate that the proposed G-BESDSP algorithm outperforms existing state of art solutions.