Yes, apparently Malta is something special. Some folks have posted articles about Maltese court cases involving scuba in this thread.
The brief version is that, throughout the world, there is generally no duty of care for a mere buddy, if you have no professional responsibility over a diver, such as a paid divemaster might have. I.e. if you do nothing to help a mere buddy in distress, you should not have any legal liability.
However, apparently in Malta there may be a different standard, such that, in one instance, a mere buddy who "allowed" his buddy to separate from him, and the buddy ended up dying; he was convicted of manslaughter, to much outcry in the diving community that viewed it as unjust. His conviction was later overturned on appeal.
Note that boulderjohn has discussed in this thread that there may be some liability attached if a divemaster proclaims some professional responsibility over another divers safety, even if they are not taking payment.