Interesting. Not exactly "DIY Home Improvement" though I have heard of people using containers to make small homes.
These are not "maritime" - this is really a standard 40' intermodal container. They are designed to move easily on ships (maritime), roads (as truck trailers) and stacked on rail cars.
There are two issues I can think of:
Ground contact - If they are on concrete (like the picture) then they are quite stable. But on dirt they may shift a bit and there may be a concern about corrosion, particularly if water can pool under/next to the container.
Level - If you are using this for anything like a workshop, you will want it to be close to level.
The solution that I have seen most commonly is to use wood to hold it up. Since it is 8-1/2' (aka 2.59 meters), 10' pieces are plenty long enough and don't cost that much. I think pressure treated wood makes sense for ground contact if the container will be in place more than a few months.
I would probably go with (US measurements) 2x4 (standard building lumber) or 4x4 (standard posts). I'm not sure how many you would need, at least one every 2 feet or so. As Harper points out, the critical points are the main corner supports - that's how containers are stacked on ships.