Unmanned vehicles keep growing attention as they facilitate innovative commercial and civil applications within the Internet of Things (IoT) realm. In this context, autonomous sailing boats are becoming important marine platforms for performing different tasks, such as surveillance, water, and environmental monitoring. Most of these tasks heavily depend on artificial intelligence (AI) technologies, such as visual navigation and path planning, and comprise the so-called Artificial Intelligence of Things (AIoT). In this paper, we propose (i) the OpenBoat, an automating system architecture for AIoTenabled sailboats with application-agnostic autonomous environment monitoring capability, and (ii) the F-Boat, a fully functional prototype of OpenBoat built with Commercial Off-The-Shelf (COTS) components on a real sailboat. F-Boat includes low-level control strategies for autonomous path following, communication infrastructure for remote operation and cooperation with other systems, edge computing with AI accelerator, modular support for application-specific monitoring systems, and navigation aspects. F-Boat is also designed and built for robustness situations to guarantee its operation under extreme events, such as high temperatures and bad weather, through extended periods of time. We show the results of field experiments running in Guanabara Bay, an important aquatic ecosystem in Brazil, that demonstrate the functionalities of the prototype and demonstrate the AIoT capability of the proposed architecture.