"Under Paris" is far from perfect, suffering from lugubrious pacing between its highlight sequence in the Parisian catacombs (where a chaotic encounter between multiple makos leads to rampant bloodshed) and a suitably action-packed final act taking place during the mayor's ill-advised sports contest, but it hits enough right beats to be worth its while. It helps that the cast generally share great chemistry, even if Anne Marivin detracts from the efforts of Bejo, Leviant, and Lyes with her somewhat over-the-top display as the aptly delusional mayor. And what helps even more are the multiple shark attack scenes executed throughout the movie, which mercifully attempt to recall the likes of "Jaws" and "47 Meters Down" moreso than cheesefests like "Sharknado", et al. This isn't to say that "Under Paris" doesn't have its moments of accidental cheese, but it's mostly successful at playing it straight.
I went into "Under Paris" with low expectations and was pretty pleasantly surprised. This movie does what a good shark movie really ought to do: it entertains without descending into self-parody and incorporates some important themes (pollution of the world's oceans and the destruction of aquatic species) without becoming a lecture. That its characters' fates don't seem set in stone and it's able to deliver a few surprises along the way is an added bonus. If it isn't quite on the level of the aforementioned "Jaws" or a couple of director Xavier Gens' other movies ("Frontier(s)" and "The Divide") it is leagues ahead of most shark movies being made in this day and age. Give it a shot; you might be surprised too.