In many parts of an ocean, there are rough parts and they are known for being rough. There are also calm waters. If you compared the oceans, the Pacific Ocean is probably the most difficult to choose an area that is the calmest because the water in the different parts of this ocean varies greatly.
However, there are areas that are very violent in the Pacific Ocean. The calmest would most likely be near the Gulf of California. Here, there are very few storms that would increase the likelihood of having violent waves. So, if you want a calm ocean and the ocean that is predictable, then you may want to pick another ocean. If you do pick the Pacific Ocean, then the calmest area is the Gulf of California.