The reason the author adds the information provided before mentioning the rescue of Angus is: not as modern as Argo but still reliable.
In the text, the author begins with a comparison between the Angus, a camera sled that takes pictures underwater, and the Argo, a much more sophisticated camera sled that can take video underwater.
During the text it is emphasized that the camera sled must be rescued, calling it an "old friend," so it can be identified that although it is not as sophisticated as Argo, it is still quite reliable and useful for his work.
If you want to learn more about Sleds, you can visit the following link: https://brainly.com/question/12287955
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