This paper presents a navigation function-based formation control methodology for autonomous surface vehicles (ASVs) operating in confined aquatic environments with currents and obstacles. Three methodological advances facilitate field deployment: (i) a differentiable approximation of the minimum distance function eliminating control chattering while preserving collision avoidance, (ii) environmental workspace boundary avoidance through virtual agents extending collision avoidance to environmental constraints, and (iii) a receding horizon waypoint strategy accommodating nonholonomic constraints and minimum speed thresholds. Unlike existing approaches requiring fixed spatial coordinates, the proposed framework allows robots to drift with currents while maintaining desired geometric patterns. Validation through numerical simulations and field experiments with Jaiabot micro-ASVs demonstrates robust performance despite GPS uncertainty, communication latency, and environmental disturbances.