Seems like the phone was using some internet access point hosted on the ship? In which case, the French naval IT services should ban certain risky services to soldiers.
it's mind boggling. personal mobile phones have potentially anyone's software running on them and that can connect to the internet means that literally anyone could be tracking and gathering who knows what data from your operation. it's an indication of the greatest unseriousness.
the location of the ship of course is not secret. but there is finer grained data about the people, the devices and what they're doing that could be gathered. and inferences made from that data. i would only allow this data to leak out if i could somehow use it to deceive my enemy.