I always take a roll of duct tape, 20 cable ties and small tools
You can get out of most situations with these, if you get a puncture you can cable tie the tire on. Also a long strap for towing.
A mobile phone in a waterproof bag and a go pro to film your bike under water.
It is always best to go out with someone else for safety and also to laugh at each other when you fall off. Plus you have the option of towing each other.