In my world there is an ocean that separates the two main continents. The problem is that I think it's impossible to navigate these waters as there are active volcanoes on the bottom of the ocean that are heating the water all the time, so it is very difficult to navigate due to the suffocating environment and the visibility problems that there would be due to the steam, plus there would be quite a lot of rain or storms in that region.
How could one cross this ocean without the use of magic? One solution I can think of is for some nation to advance technologically to create airships that achieve enough altitude to fly above the clouds of that ocean.
Any other ideas?