Kingfisher - A project in the mind

It is terrible. I tell you.
Whenever my mind drifts away in everyday life I start building the Kingfisher in my head and I always encounter some difficulties.
There are several problems which all are connected. Starting with the propeller. A propeller for a plane needs a different shape than a propeller that functions in water. I’m also thinking about a jet engine but this requires further studies. Right now I’m more into having two or three propellers on the vehicle. One for air and one or two for water. This requires two ore three engines to have enough power which again requires either one huge or several battery packs. This then leads to some gain in weight which brings us to the next problem:
The weight needs to be light enough for the machine to fly but heavy enough to be able to dive into water. A solution for this would be to make openings which allow Water to flow inside some parts of the Kingfisher. This would bring a loss of weight and therefor make it easyer for the device to sink. It - on the other hand - also makes it more difficult for the device to get out of the water again as it should be able to do.
To master the transfer from air into water we need a certain stability. The material should therefor be light, waterproof and super strong. Waiting on the surface is for amateurs. I want to fly and dive into the water with almost no delay. I was thinking of aluminum or wood but I’ll need some time to discover more different materials. Maybe there’s something printable with a 3D printer.

There’s still a lot to learn and to think about this whole project.