一篇短文改错

一篇短文改错
It was fine yesterday. The sun was shining in the
sky. I went boating by myself. I didn’t take many
friends with me because I wanted to row alone.
I hired a boat and rowed slowly to the center of lake.
A fresh breeze was blowing, fish was swimming and birds
were singing. When I reached the center, I took up the
paddles（桨）and lie down in the boat. With the blue sky
over me or green water around me I was extremely
relaxed. Over about two hours passed in this way before I
knew them. I came back home very late. I didn’t feel
tiring at all, for I had really had a good time.
请问为什么第三行的row要改成be?