Hi Cedric,
I have no personal experience as yet, but I hear very positive reactions from (professional) people who have switched from DSLR,s (and expensive ones too). Only in the rarest of occasions they will miss the DSLR, and possibly for shooting ships these could be a good option. The only thing is that I very much like a heavy camera (combined with a heavy lens) because the weight also increases the inertia, reducing camera movements either from moving your arms or from external factors such as wind. I use a 3,5 kg Canon combo (1Dx+28-300) not only for shipspotting, but I also carry it around for a weekend at the races, three days long.
Cheers
Pieter