The migrant boat sank in the Mediterranean off the coast of Greece. While a tragedy, it’s largely irrelevant to the US news. It’s not like it was a migrant boat from South America going to the US. Those do happen and they become huge news here.

The Titan submersible happened off the coast of Canada and the US and Canadian coast guards were involved. The company running the excursions is American. That’s a lot more relevant to US news.

Looking at European news, the BBC has been covering the migrant boat disaster. It’s been reported in US news too. ABC started covering it over a week ago when it first happened.

It’s also just common, which makes it less newsworthy. Another boat sank in the Mediterranean off the coast of Italy in February. https://www.bbc.com/news/world-europe-64776621

When things become common, they’re no longer as newsworthy.