You probably want to stay safe and comfortable when paddling. Here is a list by Piotr, Outdoor Explore's founder what to take on a day trip touring kayaking, canoeing, sea kayaking, SUP or white water kayaking.
The day trips are the most popular ones I do, for work; coaching and guiding and for pleasure with my friends and family. There are some elements of my 'handy kit' I take with me on these journeys.
You can watch the short film about it, recorded at the Kayak Station in Blairgowrie:
Here is the list of the kit shown in the clip;
In my buoyancy aid, you will find:
sling with the carabiner
phone (in a dry bag) and radio (sea kayaking only)
In my dry bag, you will find:
first aid kit, including personal medications
head torch and spare batteries
strong tape (for fixings tuff)
Additionally, I will carry:
pump and paddle float (both for sea kayaking or very large lochs)
If you like reading, here is a pdf document with more information on kit to carry, for personal use and as a guide/coach:
If you would like to know more about the subject or have some question, please ask, I am more than happy to help;
Happy paddling folks!