When I went to college in Jensen Beach, FL in 1969-71 I was surfing at Jansen Beach one day. Most of the swimmers were out of the water because sharks were present. I was sitting on my board when the water boiled about 20' behind me. Then I noticed the people on the beach were yelling and jumping up and down waving me in. When I got to shore they told me that all they saw was the tail of a shark but the tail looked to be bigger than me.
I never saw it but there were sand sharks, tiger sharks, hammerheads and spinners on a regular basis there. The Gulf Stream came pretty close to the coast down there.
On another occasion I was fishing with 4 other friends in an 18' tri-hull boat just out of sight of land near Hilton Head Is. SC.
I hooked a big tiger shark(about 8') and after fighting it for about an hour and fifteen minutes I got it up to the boat. I asked if anyone had a club or pistol or anything to dispatch the shark and nobody did so I forced it and broke the line. A few of the guys wanted to tail rope the shark and haul it in the boat.