I'm not aware of any test specifically for ocean shipments. However, I think you could use existing protocols as a starting point to create a pretty good test. The first step would be to identify which test procedure is the best fit for the package type and transportation mode to and from the seaport. Studies have shown that vibration during sea transport is so small that it’s negligible, so that leaves handling, stacking, and atmospheric hazards. Of course you'd want a vibration test for the land portions of the trip, but that's a separate issue. Catastrophic events (like extreme ship rolling and pitching) can occur on the sea, but typically you would not package to protect against these catastrophic occurrences.
For handling, if you think dockside loading/unloading might be more severe than other types of handling you could increase the impact velocities and drop heights found within the current procedures. You could also add a flat drop or two (to simulate handling with cargo nets), and perhaps some rotational corner drops as well. I think these “increases” would help encompass the typical pitch/roll/yaw hazards that might be encountered.
You should also consider conditioning to one or more of the atmospheric conditioning extremes, certainly high humidity. You could always add actual water spray to dampen the packages. There was a presented study 2006 that showed RH levels in ocean containers as high as 96%.
Please feel free to contact me directly with any other questions.
Source: A.J. Gruber - ISTA