They shouldn't have shown the creature in full detail in the end
They should have left something to the imagination. Non-CGI / edge of your seat moments in scary movies are the most tense and terrifying.
That's why all of the scary parts of the movie were creepy up until that point.
It should have probably ended with us seeing some dark figure within the water as the cockpit filled up with water and we got a glimpse of the bio-luminescence. That would have been WAY more terrifying imo.
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Side note:
Also, when they showed the underwater submersible, they shouldn't have shown so much light through the ice. It should have been darker and the only light source should have been from the probe itself.