Cocos was my favorite liveaboard until I had dived even better locations after. Just reaching the island is a 36h boat ride from Costa Rica mainland and usually you'd think the boat entertains the visitors for the spare days but with the Aggressor it was just you relaxing with others or on your own.

You'll reach the island overnight and admire its beauty in the morning. Welcome to Jurassic Park! The steep cliffs, cloudy forests on the peaks and wonderful animal life passing by (birds, dolphins, sharks) is a good start. One might assume this is a dive only destination but you can take the same trip and get dropped off for hiking tours as much as you want - which isn't a bad idea in practice but the diving is so good you'll "waste" your day looking for birds in my opinion and it will cost you extra for each trip.

Lucky for me only one dive operator was working during my trip because the other was busy with National Geographic, and the second Aggressor boat left after a couple of days so the chances of you seeing another dive group underwater are almost zero. Some private charters came across renting gear but they tend to also not mix with the other groups. There are "only" a few worthy dive sites such as Dirty Rock, Alceon, Dos Amigos, Manuelita, Punta Maria, but each one is so worth it. You'll be told that seeing a shark is common during every dive and yeah they dont even point out anything for you. Hammerheads and Galapagos are everywhere, in fact only 1 dive I had none of those but instead I saw dolphins instead so can't complain.

There are two regular trips onto the island. One for a waterfall and a second to the ranger station (has wifi although Claro can get you basic data sometimes if you must be reachable), from which you'll go soaking in a river which may not be downhill a pig farm so honestly that could be skipped. The waterfall is much nicer.

While I understand the costs for a Cocos trip are more than the average liveaboard trip you'll get such a great experience with the marine life and it will stay with you for a long time. Basically I tell people they should rather save for Cocos then spend on several "lesser" trips like Thailand where you'll see little underwater but you got a dive out of it... Upgrade your dive to Cocos and you'll know what I mean. The crew of the Aggressor is lucky to go diving there so often.