Is San Francisco Bay fresh water or salt water? That may have something to do with this here.
I believe that part of SF Bay is officially termed 'brackish'. Might be wrong about that. There was definitely potential for salt water corrosion in the Japan Airlines DC-8.
The big difference between the DC-8 and this B738 was that UA had a major level repair facility for the DC-8 less than five miles from where the DC-8 came to rest in the water. The repairs of the DC-8 reportedly costs more than the original cost of the aircraft. Japan Airlines had a couple issues that don't exist today. It was quicker to repair the aircraft than it was to order and receive a new/replacement aircraft. The number of available used aircraft on the market back then was basically nil. Also, carrier and insurance costs were different back then. Today a hull will be written off at a much lower costs of damage repairs than back then. A replacement B738 can be obtained from a wet lease carrier in just a few days.
Another factor - the heavy lift equipment to get the plane out of the water and the large barges necessary to move the aircraft and cranes to put the plane on the ramp area at SFO were all in place in the port of San Francisco. I doubt such equipment is available to recover and move the Chuuk aircraft closer than Honolulu or Japan. Then it will have to be transported to ?Hong Kong ?Japan. IMHO no way an insurance company is going to pay that much to attempt to recover this aircraft.
Technically possible to recover and return to the air - very likely. Financially likely in today's airline world - very unlikely.
The probably fate of this aircraft is that it will start being stripped in a few days and within a year a typhoon or other tropical storm will move it on the reef and it will break apart.
Re the A320 in the Hudson. That aircraft's keel was broken by the excessive G force of the water impact. Sully did a great job putting it down, but hit twice as hard as the A320 manual says he should of landed. IMHO, both Boeing and Airbus all engine out landing scenarios in their manuals are somewhat unrealistic. All three aircraft, the B767, the A330 and the A320 which have landed with no engine power with all passengers and crew safe hit very, very hard. Pilots will maintain all the altitude they know they can land, Then they are going to put the bird down firmly, hard. Sully was not concerned about saving the aircraft, he was concerned about getting it down near rescue boats in one piece large enough for many, maybe most, of the people on board to survive.
This water landing was almost certainly nothing like the ditching in the Hudson. Sully and his first officer knew they were going to land in the Hudson. This crew probably was surprised that they landed in the water. They likely though they were landing on the runway, and were surprised to realize that their flare put them down in the water. The Japan Airlines crew was surprised to find they were in the water.
I've made three landings as a passenger on TKK in 1973 - old shorter runway configuration. Two in the old Continental Micronesia B727 Combi - taking the island hopper from Guam to Honolulu and back. The next time was in a US Navy C-121J. The island hopper had hit a caribou with the nose gear and needed some parts and repairs. The USN squadron I was assigned to Naval Air Station Agana Guam flew the parts into the island. We had to get stopped in less than 3,000 ft because the B727 was still on the runway. We helped the CMI techs repair the aircraft and allow it to clear the runway so we could take off and return to Guam. Unless a person has experienced topical weather, it is something unlike anything we might see in the US or Europe.
I've seen a runway go from CAVOK to visibility of less than 200 ft and back to CAVOK in 15 minutes. Short heavy rains pop-up almost without notice. Sudden microburst high winds that can push an aircraft down into the water early (like DL-191) or even push an aircraft off to the side. I'm sure there are no microburst detectors at this airport, or the others in the region. The cost of installation, operation and repair is too high, and basically because every aircraft crew flying into these airports needs to anticipate that microbursts will ALWAYS be present.
When I watched the Convair 990 crash on Guam in 1973, we saw the lights of the aircraft cross the highway on a normal approach path. The rain and wind blew in, the aircraft touched down almost 600 feet left of the runway, where it had been lined up on the runway just four or five seconds before. (They were in a near zero fuel situation due to some mechanical issues and had to land or crash into populated areas.)
Yes, likely this crew tried to land and got into a situation where they should not have continued the approach. I'd wonder if they had circled waiting on better weather, or if they circled enough to get below the fuel necessary to divert. That has happened out on those islands more than once.