what a great fun swimming in the river...和what great fun swimming in the river哪个正确?

问题描述:

what a great fun swimming in the river...和what great fun swimming in the river哪个正确?
我查了字典,字典上并没有fun作可数名词的用法啊

what a great貌似一个固定用法,一个习惯用语
我读这个感觉比较熟悉觉得第一个正确