An ascent rate of 30ft per minute is generally considered safe. Judging by the description of Morrison Spring here, the “blood boiling ascent”, while frenetic isn’t necessarily unsafe because he’s only ascending from the first cavern at 35ft to the surface over a period of several minutes. The more worrisome part is when he leaves the 2nd cavern to go to first cavern between 2:50 and 3:00. This is an ascent of about 20 ft in just 10 seconds, which while a violation of the 30ft/minute rule, probably isn’t that bad considering his depth, his long safety stop and the rest of his dive profile (I still wouldn’t do it).
