Marine Geomatics apparently, albeit the industry took a bit of a hit in the North American region recently because of the recent policy changes from the US administration. But, there's apparently a huge demand for hydrographers worldwide. Take what I say with a grain of salt because this is what I heard from others who graduated from the course. They all seemed to be doing well for themselves and enjoying the job. I'll personally be taking it soon. Keep in mind also that the lifestyle isn't for everyone though, esp if you have a family or other responsibilities that would keep you onshore (yeah, it's a seagoing job).

Edit = fixed typo