We know from genetic studies that most marine species trace their roots back to the Indo-Pacific region, roughly in the area known as the coral triangle. This is the site of the world's oldest coral reefs and where the highest marine biodiversity on the planet can be found. As part of their life cycle (usually a drifting planktonic larval phase) they drift on currents, get carried by floating debris, etc. until they come to a suitable location to settle and grow up.
The trip to Hawaii was rather straightforward. The pelagic larval phase island hopped from island to seamount across the Pacific until a few members arrived on the shore of Hawaii. Hawaii's isolation accounts for the abnormally high rate of endemism (found nowhere else). Approximately a third of Hawaii's fish species, for example, are found nowhere else.
There is a twist in the journey of the Caribbean frogfish. The Panama Canal may have been manmade, but thousands of years prior to us digging our famous trench, the whole isthmus of Panama was submerged allowing for lots of species exchange between the two water masses. Like Hawaii, the organisms most likely island hopped on over to the Caribbean Sea from the south Pacific. However, once Central America emerged from the ocean in its current state, it blocked the transfer of organisms and the future evolution of a whole suite of organisms took two distinctly different paths. That's why you often see almost similar species occurring in both the Atlantic and Pacific sides of that area.
