Can't climb Tug Ladders

For some strange reason I can't use the outside tug ladders to get up onto it from the water. I just either go underwater swimming or just hump the side without any attempt to grab on. Anyone else have this issue? I've tried re-calling it and still, same issue.

EDIT: GAH! I feel so silly now. Thanks for the help. I didn't realize you had to actually hit the "enter vehicle" button. Thanks to everyone who replied.