Aside from all of the questions about the risk of DCS from the activity itself, it occurs to me that free diving mixed with scuba will affect and invalidate the off-gassing calculations from the scuba dives, unless a suitable computer is used to switch back and forth between the two modes. Along those lines, here is the page from such a computer, the Aqualung i300C.
FREE DIVE MODE DETAILS
• Although breathing apparatus is not utilized for free dive activities, nitrogen tissue loading remains a factor. Nitrogen
loading is calculated based upon a fixed FO2 of Air.
• Since a user has the option of alternating between SCUBA and free dive activities within a 24 hour period, nitrogen
calculations and the displayed value of No Deco Dive Time Remaining are carried over from one operating
mode to the other, which permits the user to maintain awareness of nitrogen absorption and off-gassing status.
• The mathematical models currently used in the i300C are based on no decompression/decompression multilevel
repetitive dive schedules.
• These algorithms do not take into account the physiological changes associated with the high pressures that
competitive type free diving can expose a diver to.
! WARNINGS:
• Ensure that you know which Operating Mode is selected (DIVE, GAUGE, or FREE) prior to
commencing any dive.
• Conducting free dives within a 24 hour period after conducting SCUBA dives, combined with the
effects of multiple rapid free dive ascents, increases your risk of decompression sickness. Such
activities may result in accelerated entry into decompression which could cause serious injury or
death.
• Combining competitive type free dive activities that involve multiple descents/ascents with activities
utilizing SCUBA during the same 24 hour period is not recommended. Presently, there is no data
relating to such activities.
• It is highly recommended that anyone planning to become involved in competitive type free dive
activities obtain proper instruction and training from a recognized free diving trainer. It is imperative
that the physiological affects be understood and the diver is physically prepared.