Yes. Sometimes it is more beneficial to move as a full round action, depending on your speed.
"Success means you may swim at up to half your speed (as a full-round action) or at a quarter of your speed (as a move action)"
So a full round action as a 30 foot move character would net you 15 feet (half of 30), but two move actions would only get you 10 feet (quarter of 30 is 7.5, rounded down to 5 feet).