An undersea Caern. Some have specific totem spirits; some are overseen by Sea or Undersea.
Grottoes function in much the same way as caems, but their depth makes them hard to reach for many weresharks.
The supernatural energy that runs through the world (called Gnosis Quintessence, Chi and a host of other names) is distributed in a rather different fashion. The energy of the world pools in various areas much like nodes or caerns; most of these are dark undersea caverns called Grottoes. These Grottoes supply raw energy to a highly specialized race of very rare creatures called Rorqual.