The CGI tsunami sequences had been shot at Kerner Optical's stages using water-dump tanks left over from special effects sequences of Indiana Jones and the Kingdom of the Crystal Skull (2008) in San Rafael, California in November and December 2008, months before any principal photography began in South Korea
The film's title is taken from Haeundae Beach, a wealthy sea-side resort area south-east of the city of Busan, South Korea. 'Haeun' translates as 'Sea and Clouds'.
"Haeundae" has the highest budget of any Korean film to date (approx US$11 million), and is Korea's first foray into the disaster genre represented by such 1970s star-heavy titles as Airport (1970), The Towering Inferno (1974), and The Poseidon Adventure (1972).
Chang Jung Lim was offed for the role of Man-sik but passed out due to schedule conflict.
The orange-handle scuba knives that Hyung-sik and the hoist operator on the rescue helicopter use are the CRKT Hammond A.B.C. E.R. A Jim Hammond design whose name stands for "All Bases Covered."