Suggestion Needed On Disconnected Landmasses

Good Morning Folks,

I need what is hopefully a quick suggestion.

I am wanting to create a set of floating islands. The main island is going to be larger. Something to the tune of 1km by 1km with at least 50% water.

Over time, during gameplay, they will be connected in various ways. either via “crashing” into the main island or docking with it in some manner that will likely increase overall size to about 4x4km.

The question I have is. How would you suggest generating them? Would it be better to create them outside the engine in modeling software? Or try and use the landscape tools?

I should add that as much as I might want to I doubt this will ever be published. It is simply a hobby of mine and I wanted to learn unreal.

Regards,
Masoric.