Sps I'd at least I think it's sps

[Delphinus]

Heliopora coerulea (as rzadun pointed out), aka blue-ridge coral. Technically it is an octocoral which makes it a closer relative to soft corals than SPS, but it has a calcareous skeleton. If you break off a piece the skeleton itself is blue which is where it gets its common name from.

The stuff tends to be bullet proof.

There seem to be two growth forms, an encrusting type and a branching type.