Had my first diving scare

[Regulated]

@davehicks mentioned the idea of cold-induced bradycardia, which I agree is definitely a possibility here. Aside from that, my first thought was a medical event that was not directly related to diving, possibly a transient cardiac dysrhythmia. Among the things you may want to consider is a cardiac workup - again riding on @davehicks ' coattails, this could be a red flag for an underlying medical condition. Although gas contamination and O2 toxicity can't be completely ruled out, the transient nature of your symptoms and their rapid resolution while still under water does not seem to suggest either of those.

Best regards,
DDM

Agree. Besides a transient cardiac dysrhythmia, consider neurological issues such as seizure activity. And “not getting cold” suggests a need for thyroid hormone studies (which, if abnormal, could help to explain cardiac rhythm issues).

Not specific medical advice to an individual—rather, general thoughts about the events described.