Moving land units from Yemen to Africa.

I see some people going from Yemen to Africa by making a defensive line and going across the water. Is there a trick to doing this?

I don't think there is any trick.

You can move units from yemen to africa easily , also from dubai to iran or from thailand all the way to timor , basically anywhere that lands are close you can move your units without a naval transport.

You can do it because those areas are in shallow waters, so the land units can easily cross and walk over.
Or, option No2 - activate Jesus mode and walk on the water