Based on the turret arrangement, gun and the glacis it is an M18 Hellcat Tank Destroyer. Used by the US military during WWII, after the war the surplus was sold to various US allies including the Republic of China. I can't say whether the turret has been remounted on a different chassis since its partiality obscured in the quicksand. There have been cases where the ROC military did remount it but since I am not an armoured vehicle specialist I cannot adequately weigh in on it. Perhaps one of our other esteemed flaired member may be able to discern this from parts of the hull that is visible.

It was likely stationed on the beach as part of shore defences during the Taiwan straits crisis in the 1950s. Since Kinmen county is right on the door step of the mainland there was a high risk of invasion by the Red Army when tensions were high. Without a serial number or more details there is little way to say for certain when the tank was abandoned or under what exact circumstance.

For technical specifications if your interested I will be happy to write a follow up on the basics.