Feet in the water and aware that he was about to commit a foolish deed, Tim crawled back to shore in sheer fright. If he had really dived after his Shadow Guide, only God knew if he would have survived more than a minute in the water.
Even before meeting Jake, he most likely would have been devoured by a predator ten times his size. In the simulations of his first and second trial, there were certainly sharks, crocodiles and other dinosaurs, but their size was rather humble. With his luck and current stats, it was not impossible for him to survive a confrontation if he knew where to strike. He might have died many times, but the challenge was not impossible, or he would never have reached the shore so easily.
But this shark... Even with his Aether Luck stat maxed, it was absolutely impossible to outrun such a predator. The sea monster would probably swallow him in one bite, just like this poor walrus weighing several tons.
BOOOM!
Tim isn't completely out of the woods yet, but we'll be able to move on to other characters now. :)