Greater Sea
The Greater Sea of Ulgrotha was the Ocean neighboring the Homelands that survived after Ravi rang the Apocalypse Chime. The ocean floor still had many fish, sea monsters and reportedly even a small population of merfolk that herded sea-cows.
Islands
Serra's Isle
The planeswalkers Serra and Feroz set up their home on a small island far away from the coast, and then proceeded to build a paradise there. Serra infused the small island with mana, making it into a beautiful and fertile place. Using his own sorcery, Feroz brought great blocks of granite and marble from the mountains of faraway worlds, and used them to build a great villa that faced over the deep blue sea. Over the two years it took to construct the house, Serra traveled across a number of planes and collected a variety of creatures that would live well on the isolated island. By the time she returned with her last trip's collection of pets and creatures, the house that Feroz built was done - great standing columns, shallow reflecting pools, and even a garden he had grown by linking with Serra's mana spell.
In the main tower overlooking the largest of the reflecting pools, Serra and Feroz then settled down to work. Studying the sole mana stream available to the world, ancient tomes on spell construction, and analyzing one of Serra's artifacts, a device that cast an incredibly strong barrier of force, they endeavored day and night for nearly a year. This resulted in Feroz's Ban, sealing their world off from the other planes.
Floating Isle
Feroz knew that whomever controlled the Greater Sea would end up controlling the Homelands, and it would be matter of a few decades before one side or the other took control. Though the sea dwarves sailed the seas, they were few in number, and weren't interested in playing watchguard. Feroz went to the Floating Island, and with the aid of his magics he built Wizards' School there, and created wells of fresh water. When the sea dwarves returned that winter, they were astonished to find a huge, castle-like structure built on their island.
Sources
- D.G. Chichester (February, 1996) "Homelands" (comic)
- Scott Hungerford and Kyle Namvar (June 14th, 1995), "Backstory for Magic the Gathering: Homelands"