Knowledge of iso-contours of the underwater terrain can be used to reconstruct it using interpolation. Identifying a set of isoclines can be more efficient and less time-intensive than sweeping a large area. In this paper, we propose a system where a small number of agile underwater vehicles cooperatively maintain a polygonal formation on a plane above the terrain and use field values measured by the individual robots to locally reconstruct the field using interpolation schemes. The formation then tracks a desired iso-contour of the field by tracking the corresponding curve on the reconstructed field.