I did some research work. The article I looked through was https://bluerobotics.com/learn/what-is-an-rov/. There are some interesting information there. I then went through OpenROV project. In India, the kit isn't commonly available. So after checking how to DIY, it turns out the BOM and building process is too time-consuming. I will probably be switching to a water-surface ROV. I will start by looking into Ivan Miranda's builds as reference and try to 3D print the same.