They don’t sink the boats, they are increasingly trying to keep them away from the border:

Europe Expands Virtual Borders To Thwart Migrants (February 2022) – [archived link]

If it were legal to deliver rescued migrants to Libya, it would be as cheap as sending rescue boats a few extra kilometers south instead of east. But over the last few years, Europe’s maritime military patrols have conducted fewer and fewer sea rescue operations, while adding crewed and uncrewed aerial patrols and investing in remote-sensing technology to create expanded virtual borders to stop migrants before they get near a physical border.

“The main reason is because the E.U. wants to step away from having proactive naval operations,” says international relations researcher Maria Gabrielsen Jumbert of the Peace Research Institute Oslo, in Norway. Physical encounters with migrants involve at least two forms of legal jeopardy that European countries are trying to avoid: an obligation to rescue seafarers and, once they are on land, an obligation to evaluate any seafarers’ claims of asylum.

In the last five years, Europe has bestowed massive new regulatory and spending power on the European Border and Coast Guard Agency, known as Frontex, which has in turn issued contracts worth hundreds of millions of euros to major engineering firms for remote border-control hardware, software, and know-how. Europe’s research initiatives, treaties, and contracts reveal an interest in peering across the Mediterranean into North African countries and dissuading or preventing migration at its point of origin. Meanwhile, legal scholars and civil-society groups are asking whether a hands-off border can really keep Europe’s hands clean.

Francesco Topputo, an aerospace engineering professor at Milan Polytechnic, Italy, who has worked on satellite-based surveillance research, says that the fate of migrants detected by his system isn’t up to him: “I would say that it’s not the decision of the technicians, of the engineers…it’s our job to give the information to the authorities. It is a problem of the entire society.”