I like swimming a lot but only have access to it during the summer months when I have more time to exercise. Because of this, I get out of condition during the rest of the year and by the beginning of the next summer I always find myself gasping for breath and barely able to complete half of what I could do last year's end.
By the end of the season, I can generally build up to the point that I can swim a mile and a half every weekday. Throughout the year I have mostly been cycling and doing pullups and chinups, although, as stated, that hasn't been working too well.
What dry-land exercises can I do in under an hour to condition for swimming?