Certified Containers are WIND AND WATER TIGHT: Guaranteed wind and watertight, meaning no leaks or holes in the shipping container with fully operational doors and minimal levels of damage or repair costs. These units can be 15 plus years in age, but has held up to inspection and still gets the â€œWWTâ€ stamp of approval. Cargo Worthy or CW containers are structurally solid. Their structure has been assessed by a certified Marine Surveyor. This assures that the container meets with all the standards outlined by its original specifications. These units come with a certificate which permits this container to be transported on a container ship. These units are generally in superior condition when compared to Wind and Watertight (WWT) containers, this is mostly due to their younger age.