YOU SAID:

Place your arm on the surface

INTO JAPANESE

表面に腕を置きます

BACK INTO ENGLISH

put your arms on the surface

INTO JAPANESE

腕を水面に置く

BACK INTO ENGLISH

put your arm on the water

INTO JAPANESE

腕を水につける

BACK INTO ENGLISH

put your arm in the water

INTO JAPANESE

腕を水に入れる

BACK INTO ENGLISH

put your arm in the water