Steven Seagull's name in real life is Sully. He lives (to this day) in a seagull sanctuary in Australia. Two extra seagulls were used to portray Steven Seagull. According to producer Matti Leshem, she added "They were all good but not nearly as good as him. Peggy was the vocal one, the very squawky bird. Gaviota (which means seagull in Spanish), I think he's almost 30 [as Steven is estimated to be about 15 or 20 years old]. The most challenging thing about Sully as an actor is that seagulls are remarkably clean. They self clean a lot, so the blood on Sully, obviously fake blood, he kept wanting to clean it off, so we had to deal with that."
Blake Lively only had a stunt double for the surfing scenes as she couldn't surf professionally, "All I did was paddle" she recalled, her surfing stunt double was professional Australian Surfer 19 year old Isabella Nichols, she taught Blake how to paddle correctly, how to wax a board and put a leg rope on and fins in to make it look authentic.
Blake Lively was pregnant with her second child during filming.
The crab that Nancy crushes while on her rock is CGI, although the crushed crab she attempts to eat is real. Blake Lively's reactions of disgust are genuine as Director Jaume Collet-Serra states "we're not allowed to harm any animal, so there were no live crabs, but we did send our art department out in the mornings to go find crabs that had died naturally on the beaches, so there's a couple of those in there."
Blake Lively was partly inspired by her husband Ryan Reynolds work in the similarly minimalist film Buried (2010), stating "that was one of the reasons why I wanted to take on this movie so much, because I know how tough that was for him and how rewarding it was."