Had to think about that a bit, then hard to choose between two. One was a self revelation about my ability or progress; realizing having put pieces together to comfortably experience, with surprising ease, an hour long chain reaction of unexpected events.
But probably most notable as it included practical as well as esthetic was my latest Manta dive. It started off with finding a Dragon Moray upon descent. Then felt I handled another divers rude and oblivious crashing into me well (wed been stationary for a while.) The DM saw it happening and was speeding over but Id calmly protected and cleared myself before he got there and I didnt let it bother me, unlike the last time someone did the same thing with no apology. We went on a tour and I kept finding wonderful things. Cool enough it was a struggle to tear myself away to go see what someone elses insistent ya gotta come see this was, just one notable sighting after another. Then back to the Manta show with quite a few eels all over people that never noticed. I felt lucky I saw the one coming to check me out, Id hate to have missed it. The best was a very, very large eel wind around the legs, crotch, torso and arms of a fellow and was traveling down around one arm towards his face while he was looking away watching the Mantas. When he turned his head front and center he was eyeball to eel snout, priceless. The cherry on top was when I settled in to safety stop and watch the over all show. Id buried my light in my BC but there was enough from the rather large number of boats it was like a full moonlit night and great vis.
Three mantas showed up, I tucked into a ball and barrel rolled inside their swoops around me. Yeah, I really liked that dive the best.