The sea floor, like the earth the humans tread in Creation, is rife with energies and geomantic arrangements. Though most of the world is land, the seas and oceans hold many resources to be tapped. In the first age, starting around the middle years with so many of the desmenses allready found above the ways, solars sent their mates and water aspect servants to scout the seabeds for them, to find more places to expand towards.
The geomancy of the sea bed is very similar to that of the land. Instead of air there is water, trees are replaced by coral and other water plants, and many different elemetally flavoured desmenses are found. Of the celestially aspected Desmenses, only a few favor Luna's chosen and none are known to be aspected to the Sun or the Stars.
Most desmenses underwater are unsurprisingly water aspected. Earth is next most common. Fire, Air and Wood are all equally rare but are found in the far north, near great concentrations of underwater plants and where the sea vents unleash heat from powerful magma deep underground.
Since the first age though, most of these manses have been abandoned. The magical infrastructure which would let one reach them easily is now gone, and few records of their locations remain. Only the lunars and certain of house Peleps know and use a few of these manses. On the plus side though, these manses were designed to be much more resistant to times passage, since creating them and maintaining things so hard to reach was an issue. Also such secret bases are almost untouchable to normal foes who would seek to destroy your sources of power.