When placed inside an immersive virtual simulation, subjects will tend to experience the feeling of being 'really there' and to respond realistically to their environment, forgetting that it is not real. This behaviour is observed when subjects experience a high sense of presence, the sensation of being in a real place and that the scenario being depicted to them is real. Here we present an experiment designed to evaluate the impact of different levels of immersion, and of different blending of virtual and real objects and body representations, on participant's subjective experience. Presence is evaluated with an innovative method combining the random introduction of breaks-in-presence (BiP) with a rapid decision-making test. Results show that the level of immersion impacts both the Sense of Presence (SoP) and the Sense of Embodiment (SoE), that the BiP has a limited impact on the SoE without breaking it, and that the level of confidence in the decision test correlates with both the SoP and the SoE.