|Anchored or underway? Neither.|
The relevant bit of verbiage from the ARRL is this:
8. All stations contacted must be "land stations." Contacts with ships and boats, anchored or underway, and airborne aircraft, cannot be counted. For the purposes of this award, remote control operating points must also be land based. Exception: Permanently docked exhibition ships, such as the Queen Mary and other historic ships will be considered land based.
Note to land-lubbers: You don't drop an anchor while pier-side.
There are legal distinctions between being anchored out and being fixed to a pier as well - it is not simply semantics. Some ships are allowed to tie to a pier in a particular port, others must anchor out a certain distance due to environmental or ecological concerns related to the ship, its cargo, country of origin or any number of other reasons.
For example, Hong Kong and Singapore require certain ships to be at least one nautical mile off-shore; ie, anchored out. If you are on Singapore's north coast, a mile anchored out puts you almost in another country (Malaysia) so the ARRL's at anchor rule to disallow DXCC validity certainly makes sense. Pier-side, there's no question as to which country you're in.
The "Exception" in part 8 (above) is noted but, in truth, it doesn't exclude other boats tied to a pier - it just includes museum ships like the Queen Mary. The exclusion is denoted by the anchored or underway categories, neither of which are true for Dom's catamaran.