Are you aware of the dozen or so rock piles, 10’-12’ deep, the County built artificial reefs on the south side of the causeway which is between the tall bridge and the small span that connects Singer Island? My brother and I were there a couple of weeks ago and there were quite a few fish on the rock piles. We were very pleased to see 50-60 juvenile conchs "speeding" across the sand bottom. When you go for a dive under the Blue Heron bridge, you should allow time to dive/snorkel on the rock piles. Google the "Blue Heron Bridge Rock Piles". Someone has prepared a You Tube video.
David