Neither of which is in the Book of Mormon. I suggest actually reading it sometime. That way you wont look so ignorant.
What's in there is equally silly...
The Book of Mormon says that the Nephites road war elephants. Probably plausible in 1830 when they were finding mastodon fossils and didn't know what they were or how old they were. Today, it looks silly. So are accounts of horses, chariots, coins, barely, wheat and other things that didn't exist in the Americas until the Europeans introduced them.
As for the Jaredites riding around in Submarines..
For behold, ye shall be as a whale in the midst of the sea; for the mountain waves shall dash upon you.
— Ether 2:24
And it came to pass that when they were buried in the deep there was no water that could hurt them, their vessels being tight like unto a dish.
— Ether 6:7
And thus they were driven forth; and no monster of the sea could break them, neither whale that could mar them; and they did have light continually, whether it was above the water or under the water.
— Ether 6:10
You do actually read your own book, don't you?