I have see many reviews by foreign tourists that either praise or really lambasts the Rosario islands and what is on offer. Here is a quick reference and just my honest opinion.
There are many tour operators that have facilities on the various islands in the Rosario group of islands. Some are better than others. It all depends on what you want to do, and what you want to get out of it. Generally, the higher the cost, the better the facility...but there are some rip-offs as well. From personal experience I can recommend the following:
* Isla del Encanto - first class place. Not overrun by vendors (there are one or two that sell beads, necklaces, etc but they don't bother you at all). Day trippers love this place, always neat and clean, lunch is very good (choices of beef, fish, rice, salads, sauces, vegetables and a juice). Beers/alcoholic beverages are for sale at hotel prices. Overnighters will be housed in clean, neat and good quality rooms, with AC, fridge and satellite TV. Only cold water shower, but you will welcome the cool water...trust me. Dinner and breakfast is scrumptious! They also offer trips to the aquarium and/or snorkeling/scuba. Be aware, if you want to spend time lazing on the beach (lots of chairs and beach beds, umbrellas and natural shade), soaking up the sun and water, then skip the aquarium/snorkelling trips as these take about 2.5-3 hours out of your 5 hour day trip. They also have a beautiful pool, some cano's/paddle boats and sometimes there is some motorised (jet-ski/boat & tube) rides. All the extras are at additional cost - you ticket includes only transfer (45-50 minutes) by speed boat to and from the Cartagena dock to the island and lunch. I 100% recommend this place!!!
*Cocoliso Island - Also well set up but not as good as Del Encanto. IMO, don't make use of the big (slow) boat, it will take all of 2.5-3 hours out of your day. Speed boat is 45 minutes one way giving you more Island Time....
*Recommendations - whenever you go to one of the Rosario Islands, make use of the fast speed boats. The big boats uses half your trip time just getting you to and from the island. The aquarium and snorkelling takes about 2.5-3 hours out of your day trip, leaving you with 1.5 to 2 hours for relaxation only.
* Use the internet to do a bit of research before booking a trip. This may save you a lot of unnecessary heart ache. Beware of the touts that sell trips at the Cartagena Docks - they are sharks!! Book online or phone, or go to the kiosks at the docks to book your trips.
* All the islands sell drinks and water, food etc - do not let the touts at the docks "scare" you in thinking there is nothing available on the islands.
* Foreigners beware - do not let anyone take you for a ride!! Use a bit of common sense. If the price is reasonable, you will probably be ok. If it is outrageous, stay away, or ask around to make sure you are not ripped off.
* Take cash along - it is just easier that way. Some facilities have credit card facilities, but they are far and few between.
Overall, the Islands are great to visit. I live in Colombia, and have visited the islands on a few occasions, and have always come away refreshed and happy. I will definitely recommend a visit!
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.