Alternate knees forward. Travel up and down jogging with those arms. Jog take arms to sides. Make little circles forward and backwards. I have funny names I use for a move you already know like the leg swings.
Some Instructors like to keep the arms in the water.
I like both. My class loves when I make them work their arms out. I really work them, then we say ahh, when we drop them to a cross country in the water. Your heart rate really jumps taking your arms out of the water. Some of the moves you can go for 8each way and drop it down to 4.