Hi all-brand new to the forum, sorry if this doesn't qualify as an incident but here goes...

I was PADI open water certified in 2011 and have about 40 dives under my belt and have done multiple deeper dives (for open water cert) having gone to 103' once but realize I am a newbie and looking for some advice here. While diving in Cozumel last week, diving for the first time in 3 years, I had an unsettling experience. We booked a refresher/shore dive with a dive master and went through it without issue.

The next morning, we were on a boat dive. All went well with descent, equalization and within 15 minutes we were at 80’. I felt relaxed, comfortable and was enjoying the scenery when all of a sudden I felt that I wasn’t getting enough air! After a few deep breaths, something still was not right, I could not catch my breath. I got the DM’s attention, when she came over I signaled that I was having trouble breathing and needed to surface. We went up to about 60’ and I was able to catch my breath. We stayed at that depth for another 20+ minutes and all was fine. We did a second, more shallow dive later that trip with no issues.

I am a 60 year old, large, (6’3“, 270lbs) man in relatively good shape and was a little shaken by this. Due to illness to my wife and a bit of nerves on mine, we did not dive again after the second, shallow dive that same morning.

Any suggestions on what might have happened? Could the tank not have been opened all the way? Do I need to get in better shape, lose weight? Thanks for any thoughts.