I think they'd run huge steel wires to points already on the seabed, and tighten the bejeez out of them. Same thing they'd do for a suspension or cable-stayed bridge
In fact, same thing they did for the east side of the San Francisco-Oakland Bay Bridge.
Very few people know that is just one wire holding up the entire "suspension" span just off Treasure Island.
It just dawned on me that this a floating rig that doesn't rest on the bottom -- duh. Lots of design info at New designs advance spar technology into deeper water. Article is 17 years old, however.