Doomnova
Contributor
Get it one day you'll be doing 4-6 dives a day for a few days and there is no sense in spending a ton of money and banging your head against the NDL on the second day.
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t-mac opined that your Galapagos trip will be a "once-in-a-lifetime" trip. Since you're already located in Ecuador, the trip to the Galapagos really isn't too far from home. I'd guess that, if you have a good time on this trip, you'll be back for more later. Considering your experience level, it might be best to discuss with your dive op the possibility of visiting easier/more sheltered sites. You can save the more challenging/exposed sites featuring strong currents for later dive trips when your skills are better and you have more experience.
Have a great time on your upcoming dive vacations!
Nitrox - ?
Nitrox can increase either bottom time or your safety factor, but not both at the same time. In other words, you can stay down longer using Nitrox then you can on air due to the increase in the partial pressure of oxygen in the mixture, however if you use this extra bottom time, the end result of nitrogen in your system is the same as it would have been on air in a slightly shorter dive.