Weird title

yeah i thought it was strange too, but seeing as i have to do a presentation on the film i tried to analyse it, so...
- octopuses can refer to many legs - there's a scene where marie goes under water and watches the synchro girls, and their legs are all doing the same thing and look quite like tenticles
- birth is like how the girls are going through adolescence and becoming women, discovering who they really are etc; they are like blossoming flowers (waterlilies!)
- synchronised swimming is meant to be a metaphor for adolescence in the film, so whilst 'octopuses' mainly relates to synchro, 'birth' is the part that relates the synchro to puberty
hope that makes sense...!

No idea, but I did notice that at the very end, Marie and Anne are lying flat on the water, eight limbs out - octopus? Probably just par hasard.