Effects Supervisor Tom Raynor comments, "Filming underwater presents a unique set of challenges. Red light falls off at a rate of approximately 1 stop every 2 meters underwater, this meant that we had to work our magic in 2D and in the grade to reintroduce colour back into the picture in post.
Accurately recreating the motion of the camera underwater also proved challenging and consequently we ended up creating a number of fully CG shots or doing take overs from live-action to a fully CG environment by the end of a shot.
The resulting tornado of fish was simulated in Houdini, using complex flocking algorithms which created a controllable yet natural fish simulation in order to achieve the look of photo reel sardines performing an unrealistic motion.
It was an incredibly rewarding experience working with the team out in The Philippines and I look forward to working with them again in the future."