Of course your suggestion is possible but let's look at it in another light.
Probably less than ten die each year from going overboard from a CLIA associated cruise ship. During that same period, somewhere in the neighborhood of over thirteen MILLION passengers sailed on those ships.
To put a viable net system that could survive the many types of weather not to mention the occaisional storm even a cruise ship encounters would probably cost well in excess of 1,000,000 dollars per vessel.
A hugely larger percentage jump or fall from bridges throughout this country. Over sixty people alone jump from the Golden Gate every year and because of that extreme number, they are going to put a net costing millions of dollars around that bridge. But to my knowledge, that is the only bridge in the entire country with such a protective system planned.
Using your justification, we would be far better served to install nets under or around virtually every single highway bridge in this country; place netting around every building over two stories tall that has balconies or terraces; place crossing barriers at every single rail crossing in the country and this, is just to name a few of probably literally thousands of protective ideas that could be done that would protect an equal or even far greater percentage ratio of people.
In light of the above, I think you'll agree with me while yes, such a system is possible, it is just not feasible.