He could have the US Navy quietly sink them, like they did back in the 80's. Subs on both sides mysteriously vanished during those days.
Where do you get your information? I'm compelled to ask because it's 100% fantasy.
The US hasn't lost a submarine at sea since June of 1968, when the USS Scorpion was lost in about 10,000 feet of water in the middle of the Atlantic. Prior to that, we lost the USS Thresher in April opf 1963 off the coast of Cape Cod during testing. Those are the last two subs we've lost.
An interesting aside: The government and the Navy were being hard-pressed by several Veteran's groups and insurance companies to find both the Thresher and the Scorpion. And it was also no surprise that the Navy and several environmental groups wanted to know the status of the nuclear reactors on each sub. Unfortunately, the Navy didn't have the proper equipment needed to search for or reach the subs.
Enter Dr. Robert Ballard of the Woods Hole Oceanographic Institute.
In the early 1980's, Ballard had asked the Navy to fund the development of the technology needed to search for the RMS Titanic. The Navy was interested in the technology, but only to help find the two lost subs. They couldn't really give a shit about Titanic. Long story short, the Navy gave Ballard the funding he needed and, after finding the two subs, Ballard went out in search of Titanic, which he discovered in June of 1985 using the new technology. The Navy had no interest in connecting the discoveries of the subs to the discovery of the Titanic, simply because the search for the subs was classified Top Secret.
In July of 1986, I was stationed aboard the USS Ortolan (ASR-22) in Charleston, SC, when we were tasked to meet the Atklantis II, out of Woods Hole, and Dr. Ballard. We spent about a week on site, with the Titanic resting on the bottom more than two miles below us. There were eight of us who were selected to "cross deck" to the Atlantis II, which allowed us to see, first hand, what the Atlantis II and the deep submersible Alvin were doing and finding. If you've ever seen the National Geographic special on the Titanic, we were able to view all of that raw footage. It was a pretty fascinating thing, and definitely a highlight of my Naval career.
One of my favorite momentoes from my career is an 8oz styrofoam coffee cup (about 4" tall). On one side of the cup I wrote my rate at the time (STG2), my last name (erased in this photo), "ALVIN'S DIVE TO THE TITANIC". On the other side I wrote the latitude and longitude of the wreck: 41° 46' LAT 50° 14' LONG.
A bunch of us then took our cups and placed them in a net laundry bag and tied the bag to the exterior of Alvin (away from any critical components). Alvin then went to Titanic. Because of the depth all of the air within the styrofoam was pressed out. Once that occurred, I was left with what you see here. I included the quarter in these photos so you could see just how small it ended up being. It's just slightly smaller than a shot glass: