My hunch is that Marlin, Swordfish, and Sailfish are different, though all are billfish. The idea of catching (and releasing) a Marlin is bucketlist legend for me personally. If I hooked one I would likely toss my rod and reel into the drink. The reality is I think I might enjoy catching a Sailfish more.
Sailfish are much smaller, but I think the "sail" makes them amazingly beautiful fish ... and they're big enough for me. The allure of these fish is why I love this guy;'s YouTube channel, "iBelongOutdoors." In this episode, he snags a few (yes, more than one) Sailfish from his jetski (a very cool and specially outfitted fishing SeaDoo, I might add). He also, as you will notice, is catching these in relatively shallow water with Miami in the background.
I think you'll like this guy and his videos.