Although anonymising the data in a crowded city is effective because of the large number of people, at sea there are fewer people, thus their movement patterns are more easily tracked.
This may sound alarming, but it is not as much. Namely, because shipping industry assets move around and because the map includes data from 2009 to 2017, the security implications are probably not that serious. However, seafarers must have in mind that their mobile phone may reveal more information than they believe.
Giving some examples of the movement patterns that the app reveals, off the coast of Côte d’Ivoire offshore operations are lit by the activities of those using the Strava app onboard. Moreover, in Togo the activity on vessels at anchorage are visible.
In another example, in Vancouver, Canada, the path of the SeaBus across Vancouver harbour can be seen. This is probably because people don't turn off their app, resulting in the app assuming that the users are exercising.
Albeit it is understood that the use of mobile phone nowadays will not stop, even if it is prohibited in certain occasions, the focus must be turned on educating people about their privacy choices, which can make a big difference.