Status Updates From Tom Swift and His Submarine...

The plot doesn't make a lick of sense, and is driven by coincidence, accident, poor planning and the malicious acts of rivals.

Convenient Eavesdrop AND an Inconvenient Eavesdrop. Low-effort plot advancement.

Right away, false urgency. They rush construction of the sub and decide not to enter for a valuable government prize in order to go after treasure - treasure that isn't going anywhere, and that nobody else can reach.

Also, anyone much older than Tom gets the adjective "aged".