One hour or more on average. The first one was 45 minutes, which I was expecting. I tend to blow through gas quickly on my first dive of the day. Dive two was 76 minutes and dive three was 83 minutes.
You’re only at about 30’, so most of that time is spent on the bottom. You'll want to do a brief safety stop at 10' to 15' to listen and make sure that there are no boats overhead or approaching prior to ascending to the surface.
The first few minutes are crazy. It took me about 10 minutes to settle in, get used to the current, and visibility that amounted to white out conditions during the winter. Once you get settled in on the bottom, start looking for goodies, and start finding stuff...you start having fun.
A bit of advice...leave PLENTY of gas reserve for the end/your ascent. You will be HEAVY on ascent: 1. You're diving 10+ lbs heavier than normal, and 2. You'll have the weight of whatever you pick up on the bottom.
Keep your eyes glued to your depth gauge on your way up. Other than your depth gauge...you have no visual reference that you're actually ascending until you get up around 15'-20' and ambient lighting from the surface starts poking through the muck. Contrary to typical good ascent practices, you may have to add gas to your wing/BC to enable you to ascend (I had to).
You'll see alligators. You may even see alligators when you're bobbing along waiting to get picked up. One floated on by in the current 30'-40' away when I was waiting for my third pickup of the day. My GoPro was of course dead by that point.

It would have made for an amusing profile and meme picture.
This is an idea of what you're looking at, visibility wise...at ~30'. Keep in mind that there's only as much light as you're seeing in this video because I've got three 1,000 lumen lights helmet mounted and a 1,000 lumen light (DRIS light) on my glove mount.