You're probably already aware, but if you ever get offered a chunk of thresher shark you gotta go for it. Cut off a steak and broil it up right and you would swear it was a good piece of swordfish.
I've heard about the great whites that hang around Catalina. The bad news is that I suspect they have been there for years and I used to go afloatin around the Isthmus in the olden days. I never saw anything except a couple of blues over there while tubing. I have heard tales of blues coming in for fish hanging on a stringer or in a basket.
I had a big pack of blacktips come in around me while I was fishing for corvina in the Sea of Cortez a couple of times. They were all less than five or six feet long, but they were biting everything in the water...including the lures I had been casting for corvina. When they got too close, I moved out onto the sand and wrestled with a few of them from the beach.
In the southeast part of the country you never want to tube at night, and not even during the day off some beaches. Bu;; sharks are totally fearless and can be very aggressive. They take over fishing spots from boat fishermen and you can't land a fish. In the surf they probably account for more shark bites than any other species around the world. Lots of bull sharks in the warm waters around Florida.
There are also some huge tiger sharks, and they are confirmed maneaters. They also favor sea turtles, and a float tuber is easy to mistake for a big turtle. At night those big tigers come almost right up on the beach. In Panama City, Florida, and other areas, they have shark derbies that routinely see folks spooled by submarine sized tigers.
On the other hand, catching lemon sharks, blacktips and nurse sharks in shallow areas is so much fun it should be outlawed. They take lures and flies and will tear up cheap tackle in a hurry. But, again, in those areas you are better off fishing from a boat platform than tempting fate.
I asked about the leopards. If you like them, you need to go north. There are favorable tubing sites at Moss Landing, Morro Bay, and around the San Francisco Bay. Most of those areas have good halibut too...and the occasional big striper or salmon.
Still farther north is Humboldt bay, near Eureka. The part of the bay that goes north up into Arcata is a commercial oyster fishery and the owners love to have fishermen catch the sharks and rays that eat the oysters. Lots of big fiesty leopards up there.
I was also wondering, Kiyo. Do you ever cook up any of those shovelnose? I used to enjoy the occasional chunk...and they are great smoked. My buddies that come over to watch football and eat up my smoked goodies thought they were some of the best yellowtail thay had ever eaten.