Hi @Lawrence,
A penetrator with a cable through it would likely be the best approach for signal integrity, but would require some kind of separate enclosure for the cable end to be protected in.
On the connector-bulkhead front the most suitable actual USB connectors I could find (beyond the DNC ones you linked to) were these, which have an IP68 rating. There are micro-USB cables in there that seem to be rated to 10m for 3 hours, but I believe they’re USB-2 only, and you may well wish to go beyond 10m deep. The standard A and C type connectors seem to just have “IP68” with no qualifier, which likely means they’re tested to 1.5m depth for 30 minutes, which isn’t suitable for a submersible.
Beyond that your best bets are more standard connectors like Cobalt Connectors and SubConn Micro Circular Connectors, although because they’re not designed specifically for USB signals they may have signal integrity issues - particularly if you require USB 3.
Is there a particular reason you need a USB connection? If you’ve got a non-metallic enclosure you may be able to connect via wifi when out of the water, e.g.
and the Droplet v2 uses a similar idea (wifi provides shell access to the control computer).