This document presents the design of Xiroi: a modular Autonomous Surface Vehicle (ASV) built to guarantee a stable and continuous Acoustic Communication Link (ACL) between an underwater vehicle and a remote computer, either located on the shore or on a support vessel. The ASV is commanded to automatically ensure a close distance for the ACL by following the submarine platform when underwater, and keeping a safety distance when it surfaces.

The platform can be operated in the following ways: (i) Autonomous Underwater Vehicle (AUV) tracking, where the vehicle is required to track a moving frame (e.g. the AUV) without the need to know the actual position of the platform, (ii) path following, where the objective of the vehicle is to achieve a number of waypoints in a time window and (iii) station keeping, where the vehicle holds its GPS position regardless of the wind or water currents.