The most popular boat trip is Trip to Elaphite Islands (Koločep, Lopud and Šipan).
These islands are car-free, so they are very peaceful and quiet.
You can read more about Elaphite Islands here https:/…
There are many places where you can rent kayak. A lot of agencies do organised tours around Lokrum Island.
Enjoy your trip!
My husband and I went last July and a boat trip to the Elafiti Island is definitely a must. We hired a private boat, and it was only $300 UDS for the entire day. Our guide was amazing and also included beer and wine. I wish i could remember the name of the company! But I know there are many like this, and compared to United States prices for similar service, it can't be beat.
I would also recommend taking the public ferries to both Lokrum and Cavtat. We loved exploring the island of Lokrum, and Cavtat was an amazing place as well. We decided to go there on our last day and so glad we did!