I just got back from my second trip to Galapagos (see my Trip review) on March 16, 2024. Our first was in 2015, when my wife and I had 14 dives under our belts. But, we both grew up on the water, and I surfed every day in SoCal. So although we weren't "intimidated" by the diving, we didn't have the basic skills and experience to troubleshoot problems underwater, dial in our buoyancy well and tended (in retrospect) to treat it like we were diving in Belize. We weren't. My wife got into trouble at depth from hypothermia and thought she could breathe without her reg in. Luckily, a DM was with her, recognized that something was wrong and brought her up to a better depth. I, on the other hand, didn't have great air consumption, but thought I handled the dives like a pro (but of course, if I had been a pro, I would have been right next to my wife and not watching a moray or something). It was cold, especially below the thermocline, down to about 60F, so it was pretty nippy. I used a 3/2 with a 3mm vest and hood, which was good for all but the coldest dives. The viz was good and the diving was epic. Fast forward to this year. 10 liveaboards, Rescue Diver cert, SSI Dive Master cert. and more than 500 dives under our belts, we went back. The viz was terrible -- 25-30 ft. The surge in the shallower dives was challenging, and on the best dives, Wolf and Darwin, the current was ripping and we had to hang on for dear life. On the deeper dives at Wolf, the temp was 60F and I used a 7mm wetsuit over a Sharkskin T2. I was toasty with that. But we couldn't see more than a shadowy outline of a hammerhead although a couple of reef sharks got within 25 ft. I loved it because it was great experience at dealing with adverse conditions, especially current and surge and sticking with your buddy and the DM had me lead the group a couple of times because someone who definitely shouldn't have been there needed one on one supervision, so I got some good experience keeping track of everyone in challenging conditions, although we were all pretty to very experienced divers.
We have been all over the world diving on liveaboards (Red Sea, Palau, Raja Ampat, Papua New Guinea, Komodo National Park, Turks & Caicos, Belize, St. Kitts, etc). A liveaboard is the way to go because you are at different dive sites all the time -- many of which are too inconvenient to reach from shore, there's lots of diving, and there's no travel time aboard a small boat from shore to some dive site. My advice is to do the Turks & Caicos Aggressor, or perhaps the St. Kitts/Saba liveaboards. They are great. Belize Aggressor is good but skip the Blue Hole, unless you want to go down to 150ft for 3 minutes for bragging rights and see absolutely nothing. I have never been bored on a liveaboard, ever. Eat Dive Sleep Repeat. 4-5 dives a day, and you will be definitely looking to dive the "bed reef." FYI, you must get Nitrox. If you do 4 dives a day on air, you will be hitting your NDL and depending on your dive computer, may be locked out for 24 hrs. Both of those liveaboards are fun, the diving is good, viz is usually good, not a lot of current to sweep you far away from the boat, and easy to get to from the states, unlike my absolute fav dive spot in the world, Lembeh Straits, where I go for at least 2-3 weeks and takes two days to get to.