This has been well studied by several groups including the US Navy, which is one of the biggest nuclear operators with over 80 reactors currently in warships. In the event of catastrophic loss, the plan is to just leave it because the oceans already have billions of tons of radioactive material and infinite capacity to absorb more.
Also nuclear reactors have occurred naturally [1] and without any serious fallout or contamination risks, showing that containment is really not that challenging. Most people think nuclear is scary because of popular science and culture, and they lack the knowledge and understanding to know any different. It's similar to people not trusting vaccines because they don't understand medical science.
1. https://blogs.scientificamerican.com/guest-blog/natures-nucl...