It is Logical to assume:

That there are UFO bases under the oceans of the world.

Why?

All the newest reports of UFOs are by the U.S. Navy Pilots. 

Where do Navy pilots mostly fly?

Over the oceans of the world.

Therefore, it is logical to assume that the UFOs coming over the oceans of the world are from undersea bases.

Imagine a space going Aircraft Carrier that has flying saucers of some kind that travel both time and space that use it as a hanger much like Aircraft carriers work.

Also, if a mother ship (Aircraft Carrier size) can travel through space and time why wouldn't it carry smaller ships (like aircraft carriers carry fighter planes.

One of the more interesting things I learned from a UFO Convention in Ventura in 2019 in the summer or fall was that it is possible that the Nazis (Hitler) from World War II used U-Boats as space ships.

I laughed when I first heard about this and thought it was the most ridiculous thing I had ever heard: UNTIL

they said that anti-gravity units were attached to U-Boats so they could fly to the moon. After that, I had to scientifically think about this more. 

For example, IF you could equally distribute the weight so the U-Boat didn't fall apart in the air from gravity on various parts of the ships then there would be no scientific reason that a submarine couldn't fly in space with the right anti-gravity units attached to it. However, you might need handles for weightless crew members to use in space and other minor modifications so your toilets (heads) on a submarine wouldn't fill the chambers with things you don't want and other modifications like this because everything is going to be weightless in space.

So, scientifically all sorts of things become possible with an anti-gravity drive of some sort even putting submarines into space and sending them to the moon or Mars.

Weight is only a problem if you are launching rockets but stops being a problem with anti-gravity units properly attached to distribute the weight of something like a submarine which is built airtight for travel underwater anyway.

For example, high speed trains all over earth are a form of electrical anti-gravity where the train lifts off the ground and travels on anti-magnets electrically. So, theoretically larger units to remove weights as large as a high speed train into space are also theoretically possible too.