Oceana is a Fab ship, been on her several times. But if its your first cruise and you dont know the places you are going to, book tours because if you go independantally and you dont know the places you are going to, if, for whatever reason you are delayed and dont get back on board before she sails, you are literally up the creek without a paddle! She WILL SAIL! Its OK for the more experienced passengers, but we wouldnt risk it. Tours from the ship are more expensive, but for novices far safer.
Sorry! forgot to say if you are not onboard for departure SHE WILL SAIL WITHOUT YOU! Many happy cruises to you.
Study your Ports of Call, glean what information you can from the net and excursion brochures and most important....pal up with a couple who have been cruising a lot of times and split the cost with them... and don't worry about missing the ship it seldom happens and only then to other people! ...Nei.
We always book our excursions through the tour company. I know they are not cheap but everything is organised for you and we have always had really good guides. As has been said a cruise ship will not wait for you if you are late back to the ship. However, she will wait if a ship's tour is delayed.
Personally I would not enjoy the trip if I was constantly worrying about getting back on time. There are people who do their own thing quite successfully but it's not for me.
We have seen people running down the quay - in San Juan - to a Celebrity ship that had already left. They were lucky and got taken out in a coastguard dinghy. Then they had to climb up a ladder to get on the ship. It looked horrendous.