There are a number of reefs north of the Gilis known for their abundance of turtles. They are huge, nearly a meter long, and some have cleaner fish attached to their backs. Lots of other wildlife, lionfish, muraines, sea cucumbers, clownfish, and more.
Walked to the more remote parts of the island, had lunch at a tranquil beach, and chatted with the locals. Amazing how so few of them know their own country, and were surprised when I showed them photos of Sumatra, Java, Borneo, Sulawesi, and other places that I have seen. (I keep my favorite 30000 photos on my smartphone.)
Magic mushrooms are widely available, and one beach dealer was pulling out a large bag of brown powder that turned out to be coffee. ATMs are plentiful on Gili Air, unlike on Lembongan, so I made sure that I have a few million rupiahs of pocket money. With 62 € in your wallet you are a millionaire in Indonesia.