I played around with the trick for a little while. It's possible to do by just standing on top of the bumper, jumping up in place aiming to land on the middle and tilt forward right before landing, then jumping near the far-edge of the bumper to make the gap. A helpful visual cue for practicing the jump is the splash of ink your squid makes from landing on a non-inked surface. Also it is possible to do this with a "full-hop" before crossing.
The jump requires relatively zero momentum using that technique but as for the method shown in the video I've found that using swim speed up increased my success rate with the jump; however, swim speed is not required. This jump is probably not going to be useful since getting hit by any form of enemy ink or swimming over a spec of enemy ink will make it impossible, but it might work since I doubt anyone would expect it in the middle of a game. Personally I wouldn't consider attempting this in a match due to the likelihood of dying but if anyone gives it a shot in live matches let us know if it is successful or unfeasible.
Note: I didn't try using any subs to test if that makes the jump easier to do (Whoops forgot! ;D). The explosion from the seeker may aid your momentum but unfortunately I did not test this.