As I write this I am sitting on a shaded sun-lounger just in front of the bridge of a boat called the Cruz Del Sur. To every horizon is water. The sounds are the wash of the boat and the hum of the engines, and I can feel a breeze that is gentle and cooling. In the distance are other boats, small and angular protrusions from the sea into the sky. Somewhere up ahead is Santa Cruz, still well out of sight, and to the north of that is Baltra. On Baltra tomorrow morning there will be a plane that will take us back to Quito. But for now there is this, the motion of the boat and the feeling of the wind and the sliver-streaked blues of the sea and the sky.

Yesterday evening I sat in this same place and watched the stars. The nights are not cold, but most of them have been cloudy. Last night though was crystalline and the stars were legion across the sky, like how they were from the desert. I wonder if we know the cost of bringing up our children in cities where we cannot see the stars. Certainly there is a toll paid in wonder.

Each of the days here has been wonderful, with ups and downs. Today we went snorkelling at Devil’s Crown, Corona el Diablo, a volcanic crater that is partially submerged, so from above the water all that can be seen is a circle of stones, a sort of distorted floating Newgrange. Beneath the water on one side there are white-tip sharks and sea turtles and a profusion of fish. We saw a shoal of yellow-tailed fish that must have been 500 strong. On the other side of the ring, oddly, there was much less life, and only in places did fish go about their daily business, poking among the rocks and occasionally fighting with each other.

Trying to get from the open sea into the inner water of the circle of rocks turned out to be more difficult than I expected, and all I managed to do was get myself caught in a strong current. That was an interesting experience. Looking under the water, I could see that by swimming with my flippers and my arms together, I could make a little forward progress. I tried swimming to either side, but I didn’t do it with enough commitment to actually get out of the current. I was never in any danger because I signalled the boat as soon as I saw what was happening, and they came and got me with the indulgent looks they save for the idiocies of the tourists, but I can see how people panic and tire. There was an edge of fear for me even though I was safe throughout; the inexorable force of the current is alien to the day to day land experience.

In the water I have now seen all that I could hope for here:  a shark turning and slinking through the deep rocks near the ocean floor; a Galapagos penguin that swam within two feet of me and then dived, showing me his hard-cornering and acceleration; a sea turtle, who at the time was far more interested in getting food from among the rocks than his fawning entourage of snorkelling tourists; and the school of fish today, which went on and on like an odd, well-attended underwater parade. It has been a great introduction to what lies beneath. The penguin is the motorbike of the underwater world, but the shark is the M3.

On occasion I have panicked and swallowed water, and then lifted my head and returned to my own world with relief. It requires courage indeed to be a scuba diver, and go so far into the hidden world that one hand can no longer be kept on the door. But I can see the attraction – the creatures below are enchanting.

The sunburn on my feet developed into angry blotchy red bands, and then those bands were rubbed by the flippers, and so now I am missing sizable amounts of skin on the top part of each foot. But I wouldn’t have missed today’s journey for the world.

This morning we were snorkelling off Floreana. There is a barrel of sorts near the beach where we landed – it’s mounted on poll and is about the size of a pickle barrel rather than a water barrel, and it’s part of a collection of heavily-signed flotsam and jetsam that has been placed there over the years so that the overall effect has a touch of the art installation about it. The purpose of the barrel is to collect postcards from tourists, so the idea is you go through the cards that are there and take any that you can realistically hand-deliver, and then you leave your own postcards for delivery by future tourists. Around the turn of the 19th century ‘real’ post was delivered this way, and ships would stop by the barrel to pick things up and drop stuff off. It’s a lovely little tradition. We picked up one card addressed to people in Ballincollig, and left a few of our own. Flicking through the cards, there were quite a few that people addressed to their future selves, talking about travel and kids and other hopes, and noting that the card should be left there as one day the planned to come back and get it.

In the afternoon we landed again and went for a walk on the island. At the coast it is hot, but there are breezes and it is bearable. Inland, the wind drops to nothing and the intensity of the sun is palpable, a burning touch. The air feels hot to breathe. We walked only a few minutes , up a winding path through a hill, and came out on the other side of the island to a beach that I think may be the most beautiful place that I have ever been. Headlands reach out on other side of it, high and steep and covered in the white trees and bushes of the island. In between the sand is white and pure, and the water green and blue, the colours melding and turning together. Turtles swim in the water and lay their eggs on the beach. Dark volcanic rocks are scattered in clumps, lending weight to the overall composition. It was on one of these that I saw for a few minutes, and I could have sat there maybe forever.

The walk back through the heat was a notable counterpoint. The German settlers who came to Floreana way back, and whose families still own many of the local businesses, were famous for their toughness, and were given awards of recognition by the governments of both Ecuador and Germany. And they must have been hard earned and well deserved. Floreana is harsh and jagged and hot and hostile, the kind of place that makes you work for every single thing that you need. The heavenly beaches at the edges are misleading, atypical, like jewels in a blade.

A week has gone by far too quickly, a pre-created routine of walking and snorkelling and eating and sleeping. Each evening the guide, Hanzel, writes the activities for the following day on a whiteboard in the main lounge. Usually we start with breakfast at seven, though sometimes it’s at six. Then it’s either a dry landing or a wet landing, the former where there are steps or a jetty of some kind to get out, the latter where we come to ground on a beach and hop out into a foot or so of water. The trails on the islands are carefully defined, and it’s not allowed to wander off them; the ecosystem here is far too fragile to withstand the tourist hordes without careful  management and control. As we go, the guide tells us about the animals and birds and plants that we are seeing. If you stand near a baby sea lion, it often comes forward and sniffs your toes. You can walk up to the splendidly-named blue footed booby almost to the point of touching and it will not flinch. The tameness of the animals is just mind-altering, the evidence of a conception I would never have believed possible.

In the afternoon we usually go snorkelling, though sometimes the order of the walk and the swim are reversed. Lunch is at 12, dinner at 7. The food has been great, rice and pasta and meat, sometimes with soup, always with desert. And by 8pm, most people are yawning and stretching and starting to think about the slow wind-down towards bed. I can see why people go on cruises, and I will definitely go on one again.

A few days ago we stopped at San Cristobal island to drop off some of the passengers and pick up some more – tours overlap, and so not everyone finishes and starts at the same time. While we were there we went to the interpretive centre, and on a wall there was a graph that showed the number of tourists coming to the islands rising to its present level of about 140,000 per year. The graph does not look entirely unlike the Google stock price, starting from near zero and reaching very high. The government of Ecuador has been doing very well to manage the increases, and on almost all of the islands there is still a sense of remoteness, of something strange and alien, much different to the feeling I was complaining about at Maccu Picchu. I hope that it can sustained indefinitely.

There are interesting questions ahead, though. What level of tourism is too much? When do you shout ‘stop’? At what point is it better to say that the days of the cheap boats are over, and from now on they want to halve the number of tourists but double the money coming in? I think this latter option is doable, and it is the one I would pursue if it was my call, despite the fact that I would rule myself out of the trip I am now finishing. The Galapagos are so special and so incredible and unique that they must be protected, even if that means slanting access in an non-egalitarian way.

Anyway. They will be problems for a new day. For now, land has appeared dead ahead on the horizon, a faint shadow, and I have to pack and get ready for the morning, and then it will be almost time for dinner. It’s sad leaving here, and I felt a sharp pull on the beach today, wondering if I would ever be back. But new adventures await.