Submersibles and submarines have been around for centuries, so what can we learn from them? How can we use them to further the goal of colonizing the ocean?

https://en.wikipedia.org/wiki/Personal_submarine

https://en.wikipedia.org/wiki/History_of_submarines

https://www.uboatworx.com/

https://tritonsubs.com/

http://www.deepflight.com/

https://www.seamagine.com/small-submarines-models.html

https://en.wikipedia.org/wiki/Supercavitation