The rainy season temperatures are usually between 26-30℃ and in the less humid part of the year, with the cool breeze, is between 20-25℃.
This part of the year is June to November, and sometimes has small downfalls of misty rain.
The currents in the Galapagos Islands can be strong, and they can affect the water temperatures usually up to around 10℃ in total. You should probably know how to dive well before attempting dive sites with powerful currents so you are prepared for them.
The average sight-range is 10-20 meters, debating on how much plankton and other microscopic forms of life. These often attract whale sharks in the less humid season.
The depths can change greatly, so it is nearly impossible to tell what average is, but it can be calculated on specific dive sights.