IF you block Gibraltar straights, there will be more water flowing from the Red Sea (and eventually, the Indian and south Pacific Ocean) into the Mediterranean, through the Suez Canal, and the Gibraltar Dam would be completely useless. This is scary and unethical at all when human needs for energy overrides any environmental concern for the life of aquatic creatures first and the life of all the land life around the mideterranean. Large rivers empty into the Black Sea, block Gibraltar and the levels of the Mediterranean may rise if Suez can not take the volume.
Not to rain on the land parade , but this is how world war 3 starts . It’s for land , oil, and power. You have the eu , African countries and the Middle East , the us going for a whole new land rush. And All the sunken treasure . Let not for get the irreversible change to the surrounding ecosystem. This is a can of worms . You don’t want to open. Just leave it be. That's not a great idea at all we know that Mediterranean sea are take part of our history then now we would about to destroy it and some of living things in that bodies of water will interrupt.
Then we have to close the Suez canal and the Dardanelles Strait as well. Ofc the transit will be easier between Europe and Africa, but the Suez Canal is sooo much more important.
The question is how stupid can you be when speaking about draining the Mediterranean Sea?. This actually happened during the late Miocene epoch part of the Messinian age from 5.96 to 5.33 million years ago and is know as Messinian salinity crisis. Don't believe me look this up.
The med is one of the most beautiful places on this planet - draining one of the main things that gives it, it's stunning looks is like asking, 'what if the sisteen chapel never had any murals painted on it', or 'what if the rainforest never existed' (we're not too far away from that last one if we keep chopping stuff down the world would for sure be a much worser place. Would it be possible other way around, to blow a "new" river from one side of Africa to another on the lowest points and connect two oceans, that would probably bring more food and lower starvation over there..