Usually the best bottom will be anywhere from 10 to 30 fathoms while catches out to 100 fathoms are not unusual. Generally, however, spring mako like the more shallow water. Bait is the second factor in the equation. I usually make my own chum from ground menhaden or boston mackerel. The reason for this is that I've found the oilier and fresher, the better when it comes to chum.
Fresh bluefish is also great to have to rig whole or in large strips.
In a pinch, anything will work, even those doggone striper filets. This method covers all layers of your slick. That brings us to the fourth factor- the chum slick. Start your slick by starting to thaw your chum when you get to the dock in the morning, not when you start fishing. This will give your frozen chum block an hour or more to soften up.