I'd reconsider the advice to not bring a snorkel, as your liveaboard may offer you a chance to snorkel with the penguins. That's harder to do if you don't have a snorkel, IMO, and a snorkel hardly takes up much weight or space in your luggage. (Take it off your mask when you're actually diving, of course
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I'd also reconsider the advice to "bring a large dry bag for your dry clothes" as you're going in the dry season to a desert island locale. As long your boat has decent a/c, indoor humidity isn't a big issue. I've been on 11 liveaboards, including 2 in the Galapagos, and never recall experiencing damp clothing. I rarely bring a dry bag for a liveaboard, unless it's a small one for keeping stuff dry on long skiff rides. In the Galapagos, the skiff rides are very short and you get on the skiff already geared up, so there's no real point in bringing a dry bag for anything if you want to eliminate non-essentials from your packing list.
I recall there were two types of landings for land tours, wet and dry. Sneakers and socks are great for the dry ones, but you might want something more waterproof in case they're wet landings.
Bring your own nitrox analyzer and you'll only have other people asking to use it, a liability since they're delicate, and definitely totally unnecessary because there will already be two aboard. Everyone else has to wait to analyze their own gas, so the only benefit to analyzing yours before everyone else is that you have more time to sit and wait for everyone else.
I wear quick dry bathing suits under my wetsuit, alternating between dry and wet when I go in for meals and such. However, they do tend to start to stink after a day or two (damn plankton-rich sea water), and washing them with soap or shampoo in the shower isn't always enough. J brings a little bottle of detergent and we soak the suits in the sink - Sink the Stink or an alternative could be helpful as well.
If you're planning on dining out during your overnights in mainland Ecuador, bring at least one pair of long pants since many restaurants require them for men.
Sunscreen, and maybe a hat if you're hair-impaired, for the land tours where it can and will get very hot and sunny. Sunglasses too, of course. Lip balm and lotion help with lips and hands damaged by sun, dry air, and salt water exposure, and I always kick myself if I forget nail-clippers, especially toenail clippers, since toenail growth can get painful if your boots aren't forgiving. I'd choose Neosporin over Vaseline for any nicks and scrapes - might as well kill some bacteria while you're at it.
I never bring a coat on any liveaboard anywhere since it's too much to pack - after all, I'm flying home to warm Los Angeles; but a sweatshirt, maybe a hooded sweatshirt can come in handy even if you're cold tolerant. Don't forget, you're on a boat with a large interior. You can always come indoors if it's too cold outside.