It's a boat, not a submarine. The low profile makes it harder to detect from the sea. Not from the air, though.
At max 2-3 knots it can only go with the current (not against). Needs calm-ish conditions, if it is to reach the destination as opposed to any random place.
I'm saying: how sure can I be that the experiment originally intended to do exactly that? Go to Hawaii?
The pickup of drugs would be the most dangerous part. No one would want to spread it immensely in space nor in time. While I'm naysaying in context of smuggling, the boat is an amazing achievement.
Made it from Cali to Hawaii, and then started on to NZ before it got crushed by something.
Still, fair distance to cover. And this was a first attempt. I'd bet there are plenty of these things out there moving drugs around.
He mentions receive contacts from drug smugglers via the website.
Edit: Looks like they've continued on building components: https://www.bluetrailengineering.com/