This experience is a great one to do while in Split! There were strong waves at the start, but it was unusual and mainly because there was a storm during the day. The kayak itself was great and we felt safe in it. The colored lights on the kayak made the experience more unique. There were two guides that accompanied the group to make sure we were safe and comfortable. They also took pictures for us so we had a free souvenir of the activity. At the end, we were even offered some local homemade cherry-based drink, which was delicious!
There were plenty of life jackets available, but they were optional, which we found strange (in our country they are mandatory, for safety reasons). Also, the two guides were always staying at the front of the group, but we think it would've been more secure if one of them was behind the group to make sure people at the back were safe.
Overall, we had a great experience and we recommend it to anyone visiting Split!