I know right? I am doing this at least a few days a week now because I'm training for the army rangers and all they care about is endurance endurance endurance....although that is changing a little because with helicopters who needs to run 10 miles
But yeah if anyone wants good "entertaining" cardio ideas this is what I'd recommend. Much funner than running by itself and if you can get up to 2 miles with 1:30 per 1/4 mile and 50 pushups, 50 situps, and 1:00 minute flutter kicks, after each lap, with no rests, you will be in baller shape.
also excellent is the "100 pullups" workout where you repeat:
as many pullups are you can do
max pushups in 1 minute
max situps in 1 minute
optional: run 1/4 mile 1:30
repeat till you get to 100 pullups
Of you can that without rest and get to 100 in 5 sets......you're going to be in damn good shape