What animal is swimming in the river that is gray and brown?
The elephant is swimming in the river.
    src        edge_attr  dst
0     0   to the left of    4
1     0   to the left of    3
2     0        on top of    2
3     2        wading in    1
4     2         lying in    1
5     2      swimming in    1
6     2           inside    1
7     3          wearing    5
8     3          holding    0
9     3        riding on    2
10    3         carrying    0
11    3       sitting on    2
12    3          wearing    4
13    3          wearing    7
14    3           riding    2
15    3     sitting atop    2
16    3  to the right of    0
17    4  to the right of    6
18    4  to the right of    0
19    6   to the left of    4