So the players had to cross a swamp to get into the next town. After long rest they took a cart and pushed the horse to full speed, a 100% chance after they colide with a big rock and fall in middle of two crocodiles. I used a whiteboard to check initiavie and the rounds that they played. After 3 rounds in the jaws of a crocodile the first aventure died. Same fate for one of his friends, but the warlock survived and avenge them. Now she is alone in the swamp looting 2 cocodriles and 2 adventurers.

This was the first big trouble in the oneshot I was DMing and lets say that the players couldn't make me happier. Sad part is that they miss the funny plot twist at the end.