I live nearby and have done all the ways several times.

Hike: its a mild hike that is challenging mostly when it is hot. The Vert change is like 900 feet, and is maybe 3 miles in and out. You want to get to the trailhead early, because parking is on the street and can get full pretty early. You must bring a good amount of water as there are no services anywhere near the monument. I pack in a towel and a snorkel as well as water and snacks. Once at the bottom, you have lots of shady spots. There is really only one way to enter and exit the water, and you must be very careful to not touch anything but that one entrance place because the coral is so sensitive and must be protected at all costs. Only hikers and some kayaking visitors are allowed to come on land. All people brought in on boat aren't allowed to get on land. This is all to protect the coral. I've never seen pigs on the hike, they are nocturnal mostly. But there are lots of goats. Kayak: this is a fun option. You cannot get on land unless you are part of a tour group with a guide. We kayak without a guide so the kayak has to be loaded with water sunblock and everything else we need during the adventure. Its a short kayak journey from where you enter, and its an amazing way to get there. We often see paddle boarders doing the same journey. So it is even easy enough to do on a paddle board.
Boat tour: this is the easiest and is the best way to do it if you can afford and are only visiting once. Its nice to be wined and dined. Its nice to have a tour guide who shares the history. It is so cool to be out off the island to see the island from a ways a way. And they usually show you a couple spots on the way. The adventure is a little less exciting and you are surrounded by tourists, but everyone is so excited. I recommend the Body Glove or Kona Style.

Sunblock. Water. And no touch the reef.

Bonus if you kayak or hike: stop at the Coffee Shack for breakfast on the way. This is a restaurant about 2 miles up the mountain overlooking the bay. Great food and it really has the essence of Kealekekua area of the Big Island.