When Elizabeth took off her shirt in truck, it looked like she was wearing a bikini top without straps. When she gets in the water, it looks like it was painted on with fancier areas where straps are.
When Cam takes off his suspenders to jump in the river after Elizabeth, his suspenders reappear on his shoulders while he's in the water.
When Locke slows the train down so quickly, it would have thrown everyone on it forward very violently. They did not even stumble.
Elizabeth - the mermaid - said that she got her legs during low tide. The water will either attain high tide or low tide in 6 hours and 12.5 minutes. In other words, the tide takes 6 hours and 22.5 minutes to get low after there has been a high tide, and high after there has been a low tide. Low tide lasts between 20 to 30 minutes after its occurrence. Yet, she spent hours upon hours in her legs with no explanation otherwise.
Netflix said Elle is Cam's sister, not niece as described in story.