Some fishermen won't care as there are less ships where the cables are, they'll fish there. There are a lot of cables and fishing vessels in the Irish Sea.
Security concern is the more unlikely scenario of accidental cutting. There is enough redundancy that it is very difficult to cut them all for a single ship and if there are hypothetically multiple ships all cutting at the same time, then it is likely to be traceable. The cost of cutting these cables by sending someone out there is significant enough in addition to how unlikely they are to succeed.
This book isn't actually appropriate for toddler age children, but there is a "sequel" that focuses on toddlers. While there are some nice ideas in the book, it tends to ignore the most challenging parts of parenting. If you're going to spend the time reading a parenting book, I'd recommend a research-based parenting program.
