I have studied ditching in some detail, and know ferry pilots who have related their actual ditching experiences to me. They were lucky, one being pulled off the Arctic ice before freezing to death. Another, who had ditched at least twice before, ended up with a permanent disability from his injuries when he put a BN2 Islander into relatively calm water. On another occasion I was flying a DC3 over the North Sea when I heard someone putting a Cessna 172 into the drink. They knew roughly where he was, but he did not survive.
Even with this knowledge, I have also taken plenty of unnecessary risks in my time, including flying a Jabiru-powered Sonex across Bass Strait several times. The last trip cured me of such risk-taking forever. Low cloud forced me down to below 500ft and the sea was far too rough for any ditching to have been survivable. I consoled myself in the knowledge that if the impact did not kill me outright, death would be quick in such cold water.
Were the pilots of the two DA 40s fully aware that a night ditching is unlikely to be survivable unless executed with considerable skill and into calm water?
Were they fully briefed on the risks, and on minimum altitudes required to have a hope of gliding to land? Who sent them out there? Someone may need a smack on the bottom.