Grand Sea River

The Grand Sea River is a high speed current located in the northern section of the Great Sea. It's roughly 50 miles wide, and about 500 miles long, and is powered by a string of high energy undersea thermal vents that set up a high intensity thermal convection underwater that powers the river and creates the extremely fast flow rate of up to 17knots as a result. This hydrothermic flow of water acts very similarly to the Jet Stream, and can increase the transit speed of ships by over twice their top speed, assuming favorable winds. The fastest recorded top speed observed by any ship operating within the river is 32knots sustained. However, despite the incredible east to west speed advantage that this current creates, most boats avoid it. Only the bravest, or most desperate captains risk it.

This is because the waters within this inner-sea river are always tempestuous and stormy, creating great navigational difficulties for any ship that enters it. Plus, due to the difficulty in sailing through these waters, only the larger ships venture into this area, as the smaller ones aren't rugged or durable enough to stand up to the constant, hurricane like abuse suffered by wooden vessels passing through the river. Due to this continually tempestuous state, there are more shipwrecks within the small space of the river than in the entire rest of the Great Sea.