Nautilus Explorer Liveaboard
I was fortunate enough to be in Guadalupe Island in 2018 on the Nautilus Explorer. We sailed in the end of July and it was a trip of a lifetime! Guadalupe is a little difficult to get to - it's a 3 hour bus ride from San Diego to board the ship in Ensenada, Mexico, followed by a 20 hour sail to reach the island. The crossing can be rough when winds/waves are up...but when you arrive it's all worth it! You are anchored in the leeward side of the island so the ocean was as smooth as a swimming pool the whole time. You could actually see the sharks pretty well from the deck!
We had sharks there all 3 days, all day long every day. There seem to be more sharks there than in the past? According to the crew, the seal populations have increased over time and have allowed the sharks to do the same. The sequence on day one starts with alternating 1 hour in a cage and 1 hour out so that everyone gets equal time in the cages. However, starting on day 2, the cages were not always full - so you could stay longer if you wanted. The water in late July was as warm as it gets - mid 70's F - so you need a thick suit/dry suit to maximize time in the water.
As for the ship, the food was good and the staff was great! Very energetic bunch and they took care to make sure we were well taken care of. Would highly recommend it!
Bottom line - if you have always wanted to see Great Whites, this is the BEST place in the world to do so. The visibility is as good as it gets there (80 - 100 feet?). Keep in mind that in cage diving you have only a wetsuit and weights - no BC or tanks - so you can expect to wear 30 - 40 lbs of weight just to be able to submerge. Also realize that there is nothing else to see in the water when the sharks are not around, so there may not be something to see all the time. Even so, one of my best memories of the trip is sitting in the cage by myself at the beginning...waiting...and then having a massive shark shoot up at the bait right in front of me! Hope to visit again someday...