In the past, The Deep has been characterized as a bland and vain figure who is looked down upon and looked down upon by those around him, but throughout The Boys there have been hints that his aquatic powers are more than what his peers realize.
The Boys season 2 finale set The Deep up for an entirely different arc in season 3, which might finally reveal the true nature of the Super’s power – he’s psychic.
It would be an appropriate humorous twist for The Deep to discover that its affinity for fish and other aquatic creatures is rooted in an innate telepathy that only works in the relatively simple minds of such wildlife.
The Church of the Collectives did indeed rescue The Deep in The Boys season 2, but why they did so remains a mystery. It appears that The Deep will take over the Church which could reveal why he was wanted by the church.
If The Deep has a telepathic connection to aquatic wildlife, then you may be able to learn to develop those abilities and possibly even apply these powers to human targets in The Boys Season 3.
The story of The Deep and the Church of the Collectives is not in the comics, which means The Boys can continue to develop this plot as the writers chose, including completely reinventing The Deep.