The problem of monitoring water to guarantee its integrity is recognized as one of the urgent issues to be addressed in the near future. Thanks to recent advancements in technology, the use of autonomous, low cost, mobile sampling systems, potentially cooperating in a network, appears to be a feasible solution for monitoring aquatic environments. These systems are promising substitutions to the currently used buoyed devices, research stations and vessels through offering more widespread samplings, giving better synoptic views of water parameters, with less investment in human resources and facilities with respect to traditional methods. In this paper, we present a robotic platform as a floating mobile sampling node for an aquatic monitoring network: the robot is solar-powered, amphibian and modularized. In particular, we present the development of the first prototype used to evaluate the design and to investigate amphibian locomotion, navigation and energy issues.