Saw a couple of tiger sharks on scuba dives years ago. One was during a day time dive, and there was about 10 of us there, and we followed it for a while until it sped off. About 1.5 to 2m long or so I’d say. Heart was fairly pounding seeing it though, was really cool. Second time was on a night dive, only 3 of us on it, but that was freaky, as night time is their feeding time by all accounts and it was harder to see around.
Did a snorkel on the West coast of Oz with hundreds of whale sharks around. Manta rays as well. Good experience.
Saw a basking shark around home one time in the local fishing docks. Looked like a big dopey fish more than anything. One washed up on a beach around a couple of years back.