It will always be as leaky as a sieve, if it gets built at all.
Immigrants storming into Europe in masses like that meet a european population whose willingness to take them in decreases rapidly....and the EU has the money, the pressure is rising.
Look what tiny poor Greece build on their border to Turkey, alone!
There is nothing leaky about it....
Your country, BB, doesn't have much coastline; the country I come from is all coast.
Yes, but they all want to come here....."Germoney"!