Via Nerdist.com:

When you’re the only human on an island in the middle of an ocean, you have to learn to take care of yourself. In The Last Jedi, we see Luke Skywalker do so by using the natural resources on Ahch-To. He catches fish, he probably roasts porgs (I’m just being realistic), and he squeezes green milk from the thala-siren. The vivid scene isn’t gross to anyone who’s been on a dairy farm, but it caught Rey and some fans off guard. We asked creature shop head Neal Scanlan about bringing the scene to life, and he told us it’s all practical…and involved a helicopter.

“At the very beginning of the film, Rian [Johnson] said to me that he wanted to take animatronics and practical effects and put them there on a real location—he didn’t want to do certain things in the studio,” Scanlan explained. “We went to that location, we photographed that location, and we created a digital map of it so that later back at Pinewood we could recreate the rocks. When we sculpted the thala-siren—she’s a full-sized animatronic puppet and she’s about 18 feet tall—she was sculpted to fit into the rocks so that she actually looked like she was sitting in that environment.”

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