OK this took a while. I don't know if this is the shortest solution.

1st couple - H1 W1
2nd couple - H2 W2
3rd couple - H3 W3

1. H1 and W1 cross to the other side.

h2 w2 h3 w3 ----- h1 w1

2. H1 comes back.

h1 h2 w2 h3 w3 ----- w1

3. W2 and W3 cross.

h1 h2 h3 ----- w1 w2 w3

4. W1 comes back.

h1 w1 h2 h3 ----- w2 w3

5. H2 and H3 cross.

h1 w1 ----- h2 w2 h3 w3

6. H2 and W2 come back.

h1 w1 h2 w2 ----- h3 w3

7. H1 and H2 cross.

w1 w2 ----- h1 h2 h3 w3

8. W3 comes back.

w1 w2 w3 ----- h1 h2 h3

9. W1 and W2 cross.

w3 ------ h1 w1 h2 w2 h3

10. W1 comes back.

w1 w3 ----- h1 h2 w2 h3

11. W1 and W3 cross.

nobody left ----- h1 w1 h2 w2 h3 w3