Nowadays, autonomous intervention is getting more attention in the underwater robotics community. Few re- search projects on this matter are currently under development. In this context, and after a first successful experience in the RAUVI Spanish project (2009-2011), the authors are currently involved in the TRIDENT project (2010-2013), funded by the European Commission. To succeed in autonomous intervention, an AUV endowed with a manipulator and with a high degree of autonomy is essential. The complexity of the required robotic system is very high and the system integration process becomes critical. This paper presents the problems being solved in TRIDENT, from a systems integration perspective. As a case study, some results, achieved during the last experiments carried out in the Roses harbor (Girona) in October 2011 will be presented, to demonstrate the capabilities exhibited by the AUV for Intervention under development. The experiments were focused on the problem of autonomously searching and recovering a black-box mock-up that was previously thrown to an unknown position. This paper presents the hardware and software integration aspects that were necessary in order to address such a challenging problem.