No. "Deep Seas" provinces always also have the "Seas" tag. So any site that can be found in a "Sea" can also be found in "Deep Sea". I made the same mistake
here originally, but I've fixed it now.
Also, there are no S4 sea or deep sea sites. Chris, what S4 site do you think can exist in seas? Or N3? or F4?
Highest site level in seas from Edi's DB:
Non-unique: E3, A3, W3, S3, F1, H1, N1, D1
Unique: N2, D2
(There are S3/?3 unique deep sea sites, but it's irrelevant, because there is also a non-unique site at the same path level.)
Highest site level in deep seas (including "seas"):
Non-unique: E3, A3, W3, S3, F1, H1, N1, D1
Unique: N2, D2