The spot you show in the water (100 feet marker 67 ? ) if i remember right is probably a US landing craft (victor 2 ) ) that was used to attack the other location you marked inland (Cave made by Japanese ) . What was described to my dad by fishermen .. If not that It could be one of the 6 US pt boats . the fishermen said its not a big boat . If its japanese its very small or row row . What they Said its not a US CPB , not a Jap cruiser , nor a Hospital ship . If i remember right the mark 8 were were in the 70's mileage marker area. Where am looking is off the Siaton river area in deeper water . Last place the CPB , Lt cruiser , and the hospital were seen . Im figuring there was a big cover up on what really happened with one of those fast craft may be friendly fire ? So during the war with censorship nothing ever sunk in this area . That Pt 41 guy is famous for cover ups here and korea . Am trying to find the exact base for the CPB might of been pirates cove siaton . And those fast boats was Zamboanguita . Good Luck