这是两个意思相同的句子吗?
she swimming across the river 这句是错的,swim不用加ing,可以用swim的过去时等等啊!
she is swimming over the river 对的.
（这一处over和across都行,只不过有细微的差别而已,你可以去瞧瞧over与across的区别!能查到的）