Arriving off the mouth of Moro Bay in the afternoon, the ship lay to until the following morning, 9 December, when she entered the bay. An explosion ahead of the ship sent the American bluejackets to their general quarters stations before it was discovered that the local fishermen were just out dynamiting for their catch. The ship found a PBY awaiting her arrival and commenced tending operations. Three more Catalinas arrived later in the afternoon, as well as two OS2U Kingfishers which had been attached to at Balabac. After being informed that Japanese troops had landed north of Gagayan and were marching overland to Police, the ship prepared to get underway and dispatched the PBY's on patrol over the Celebes Sea. Leaving word that the planes were to rendezvous with the ship at Tutu Bay, Jolo, "William B. Preston" got underway on 10 December. The ship arrived at Tutu Bay later that day and found the PBY's awaiting her, after having found no trace of enemy activity during their patrol sweeps. At sunset, a veritable procession of masts and funnels moved across the southern horizon; and the men on the "William B. Preston" could only guess to whom they belonged. The following day, the planes were again sent out on patrols while the ship upped anchor and proceeded for Tawi Tawi, receiving word en route that the PBY's were to return to Lake Lanao in Mindanao and the OS2U's were to rendezvous with the ship at Tawi Tawi. Although she had never hoisted aboard any aircraft before, "William B. Preston's" bluejackets rigged up a crude cradle between the two 50-foot motor-boats aft and provided padding for the Kingfisher's center float with mattresses and life jackets. One OS2U was taken aboard and berthed in this fashion while the other was towed astern. Smooth seas and a 15-knot pace facilitated the towing operation, and the two planes arrived safely at Tarakan, Borneo. Met by two Dutch destroyers, "Kortenaer" and "Witte de With", the seaplane tender made port at Tarakanbut was soon underway again, this time for Balikpapan, Borneo, joining many ships from the Asiatic Fleet (, , , , and "Heron". Two hours after arrival, the ship received orders to accompany the small fleet to Makassar and got underway on 13 December.