It's very interesting swimming.怎样改正如果用it开头要怎样修改 ，还有我想知道它错的原因。

It's very interesting swimming.怎样改正
如果用it开头要怎样修改 ，还有我想知道它错的原因。

it's very interesting to swim.

Swimming is a very interesting sport .

Swimming is very interesting.

It seems very interesting to swim。