NAVD88 depth (US Feet) - EPSG:6358

WKT

VERTCS["NAVD88_depth_(ftUS)", 
	VDATUM["North_American_Vertical_Datum_1988"], 
	PARAMETER["Vertical_Shift", 0.0], 
	PARAMETER["Direction", -1.0], 
	UNIT["Foot_US", 0.3048006096012192]]

WKT2

VERTCRS["NAVD88_depth_(ftUS)", 
	VDATUM["North_American_Vertical_Datum_1988"], 
	CS[vertical, 1], 
	AXIS["Gravity-related height (H)", down, 
		LENGTHUNIT["Foot_US", 0.3048006096012192]], 
	ID["EPSG", "6358"]]

Data from @esri/proj-codes

{
  "wkid": 6358,
  "latestWkid": 6358,
  "macro": "PE_VCS_NAVD88_D_USFT",
  "name": "NAVD88_depth_(ftUS)",
  "wkt": "VERTCS[\"NAVD88_depth_(ftUS)\",VDATUM[\"North_American_Vertical_Datum_1988\"],PARAMETER[\"Vertical_Shift\",0.0],PARAMETER[\"Direction\",-1.0],UNIT[\"Foot_US\",0.3048006096012192]]",
  "wkt2": "VERTCRS[\"NAVD88_depth_(ftUS)\",VDATUM[\"North_American_Vertical_Datum_1988\"],CS[vertical,1],AXIS[\"Gravity-related height (H)\",down,LENGTHUNIT[\"Foot_US\",0.3048006096012192]],ID[\"EPSG\",\"6358\"]]",
  "description": "NAVD88 depth (US Feet)",
  "authority": "EPSG",
  "version": "8.2.7(10.3.1)",
  "deprecated": "no",
  "areaname": "USA - CONUS and Alaska - onshore",
  "extent": {
    "slat": 24.41,
    "nlat": 71.4,
    "llon": -168.26,
    "rlon": -66.91
  }
}