This Trial... He had already passed it.
With his Spirit Body deployed, Jake was now able to spot the closest life forms and adapt accordingly. It was far from perfect, but it was incomparable to the previous situation. He was no more afraid of sea creatures than he was of land creatures. What he really feared was the unknown and the feeling of powerlessness. With this new asset in hand, he could now gather information in advance and orient himself.
Sadly, he didn't yet master any mental techniques. There must have been all sorts of skills using the Spirit Body or his Aether to analyze his environment, but they were out of his reach.
Jake had memorized all the Aether runes in the manual, but most of them were useless without being connected to the others. Like the letters of the alphabet, more were needed to form words and then sentences. Some runes had powerful effects by their mere existence, but they were of no use in his present situation and would instead cost him a lot of energy and effort.