This episode is brought to you by XDEEP and the patrons of Speaking Sidemount. Huge thanks to both for their support. In part 2 of my discussion with Prof Simon Mitchell, we get into the negative impact of increased gas density, particularly at depth. We muse on the impact of gas density and CO2 retention with it likely being a factor in dive accidents such as that of David Shaw, and then I get to rant a bit and ask Simon about the benefits of streamlining with respect to work of breathing. From there I ask Simon about the relationship between CO2 and panic relating my thoughts on the relationship between the psychological aspects of an issue in the water and the physiological responses to these stressors. Simon gives some advice for divers in a panic situation and also for rebreather divers faced with a CO2 issue. We hit on some misconceptions or poorly understood areas such as reverse profiles, the issues with multiple deco dives in one day... We talk NDL for recreational divers and what it really means, we chat about free diving after a scuba dive and then Simon shares his extensive experience on applying human factors in the surgical operating theatre and how human factors apply to diving.