Curacao and Bonaire are the wrong places to see big stuff. They're known for macro life.
Southern Belize has most of what you want - Whalesharks, (only specific weeks in spring after the full moon) Reef sharks, Hammerheads, Eagle Rays, occasional Mantas - no sea lions though. Afaik it's the only place in this hemisphere that you can
dive with Whalesharks - at Gladden Spit - it's also 80' and blue water diving. This will give you a far better idea of what to expect than I can:
Avadon Divers - Placencia, Belize -- Reef Adventures Some of the AI's on the nearby atolls also run optional $$ trips to Gladden Spit.
Caribbean Reef Sharks are almost a given at Stuart Cove's on Nassau - they feed them during daily shark dives. The sharks also hang around some of the shallower wrecks nearby during non-feed times. A lot of the dives in that area are 30-80' or so.
But I agree with Robin, they're different in the wild. Much more interesting and usually just going about their daily routine. At shark feed sites - even during non-feeds, the sharks always seem to be circling looking for a handout.
Whale shark's are snorkel only off Utila and Holbox - part of their marine park/conservation rules. I know, we did a Whale shark survey/study week at Deep Blue a couple years ago and met/dove with several experts in the area.
We saw the biggest Eagle Ray I've ever seen in my life on a night dive off French Cay in the Turks/Caicos last spring. And multiple stingrays - they often let me get within 5-10' or less. Probably a dozen barracuda and about 4-5 reef sharks on every single dive (8 of them) over two days. I must've followed one around the reef filming for about 10mins. one day. There's a 6000' wall nearby so big pelagics often feed in the shallows. Saw quite a few sharks off West Caicos wall also. In less than 60'.
Around 2004 we shore dove Grand Cayman. At Eden Rock (40' or less) a group of about 10 Eagle Rays flew over. Later that week at Turtle Reef (50' to the sand) we saw another group. There's also several hundred large tarpon that hang there during the day - I just read a recent report - they're still there. And there's Stingray City, can't get any shallower than that - 15'.
And I saw a couple big sharks off the North Wall but we were deeper - like 95-100' - and they were maybe 200' below us. The water there is ultra-clear.
We're looking at Tobago next year. It's rougher water diving but Mantas are pretty common.
Manta Lodge in Speyside is one clue...lol And Hammerheads from Dec-Mar off the Sisters - a pinnacle that's about an hour (two?) from Speyside.
We often see small reef sharks off Maui - often near Molokini. In the late afternoon my buddy saw Mantas nearshore to Maui - but they didn't get close. Turtles are a given at some sites - at one of them (St. Anthony?) they sleep there.
There's also big turtles off South Kauai near Sheraton Caverns. Very rarely you might see a Monk Seal off Kauai - they're endangered and extremely protected. And there's the famous Manta night dives off Kona.
The only other warm place I know of for Seals/Sea Lions is San Pedro, a small island off San Carlos (Guaymas) MX. USAirways flies there regionally from here - it's a long weekend place - kind of a sleepy little town. There's a seal rookery there and they always hit the water as soon as your boat moors. I've had them chase me, blow bubbles while admiring themselves in my housing port, and stay just out of reach while I'm swimming nearby. It's really shallow - 20-40' near the rookery and you can actually swim right up to and chase them out of the water. Leave your snorkel and any dangly things on the boat.