Late to this, I agree. It does cover some familiar tropes, but the context in which they unfold is, no pun intended, suffocating.
As for the use of silence, honestly, I think it would've been even more effective without any spoken lines after they jump in. The underwater ambiance and pensive, subdued soundtrack underline the tension very well.
Be mindful if you suffer from thalassophobia, though. Mine is somewhere on the moderate side and I still got full-blown anxiety during several sequences.