At around 18:00 into the film, the two spears in the plesiosaur's neck disappear.
At around 56:00 into the film when Sanna throws a stick to her dinosaur "brother", the stick clearly hits the ground. In the next frame, she is running away and the stick is still falling.
At around 1:11:00 into the film Tara is wearing a rope, then suddenly it disappears.
Dinosaurs had already been extinct for millions of years before human beings in their now-recognizable form first appeared on Earth.
Plesiosaurs never left the water, even giving birth beneath the waves. They fed on squid and other small animals.
At around 51:00 into the film when the baby dinosaur hatches from the egg, you can see that the egg is made from fiberglass and the fiberglass mat that was used in it.
When Tara first rescues Sanna from the ocean, it is evident that the actress playing her, Victoria Vetri, is lying on a flotation device, as her feet and ankles are sticking up backwards above the water.