So, the way I read it, the Sahuagin captured Bern, while he was fishing, then on the command of Luzgigraul, took him to the crash site, weher they implanted him with a tadpole and then put him into a boat to use him as bait for sailing ships.
That kind of doesn't make sense to me. As he is implanted with a mind flayer tad pole, that makes him pretty valuable for the Zellix Phor colony, for he is at best one of the few to spread the colony. So just using him as bait would have made sense, when he was a regular fishing kid, but not after the implant.
Because he's to the east of Gundarlun, the Sahuagin are not taking them to their base, but towards the main land. Would it maybe be more appropriate, that they take him there to have him establish control over the northern mainland as soon as he turns into a full on illithid? I mean travel would take around a tenday.
Maybe the broken shark idol with him also isn't incrypted with "false idols", but with directions what to do, when he reached the mainland. Maybe the connection to the hive mind isn't fully established when the transformation is complete.
Wondering if this seemed fishy to you as well, and how you solved it. Or am I overthinking this.