To reproduce: Use a transport beam to teleport to a building which resides on a megastructure. It will usually place you below the megastructure.
I say usually because the only time I wasn't placed on the ground/underwater was on an aerial floating platform on a gas giant. I've tried it with both sea and aerial platforms on several other planets and it happens consistently on those. For whatever reason, gas giants seem to be exempt.
I say usually because the only time I wasn't placed on the ground/underwater was on an aerial floating platform on a gas giant. I've tried it with both sea and aerial platforms on several other planets and it happens consistently on those. For whatever reason, gas giants seem to be exempt.