Even though much of Europe's sub-sea cables to N. america pass through Irish waters, it seems we do not have any ability to see underwater now - even though we could for 3 or 4 decades last century. 'Tis too expensive now, it seems. Quote:
“Almost all of the Irish navy’s ships had sonar between the 1960s and 1980s and the former flagship vessel, LÉ Eithne, had it until the 1990s when it became defunct and deemed too expensive at the time by the Department of Defence to replace.”
https://ukdefencejournal.org.uk/british-warship-chases-off-russian-sub-from-irish-harbour/