What to carry as spares/back up

Hi all!

I am getting together a small dry box to carry in the ski hatch and saw something a while ago with some tips on what to put in it, but for the life of me now I cant remember!!

Please help me....

So far on myself i would carry:
Whistle
Pencil flare
Phone in a dry pouch
VHF radio

In the box:
Spare whistle
wedge in case of rudder cable failure
Reflector tape
???????

First Aid Kit
Separate own dry bag so its easy to grab

Thanks in advance!

For safety I carry -
Mirror
Whistle
Flashlight
Phone in dry pouch
Bungee and dyneema loop for emergency rudder
(Plus im always in an appropriately thick wetsuit, wearing blaze orange, always use a leash, and have reflective stickers all over everything)
Only on big days I also carry a PLB
I have been meaning to get a VHF radio too, but havent yet. That is very handy to have.

I carry all those things on my PFD. As you mention Dry Box, in a worst case scenario like you're preparing for, it could be reasonably expected that you are separated from your boat with no warning. Ideally you'll have as many of these items attached to YOU as possible.
A friend of a friend tragically died after his leash broke, boat blew away, and partner didnt have a phone. The swimmer had a phone...in the hatch of his boat. Just saying you have the right idea, but always have at least 1 communication device physically attached to YOU at all times in medium-big conditions, in this case your phone.

When bad things happen to experienced people it is usually a chain of failures, so assess where the weak links of your chain are. You're on the right track though.

Maybe add some duct tape, for emergency repairs.

I should probably up my safety game, but coming from a sea kayak background I appreciate  the simplicity and minimalism of a surfski. When on the sea kayak I always had a lot of safety/emergency "stuff". Now that I paddle a surfski I usually only carry the minimum safety gear like a whistle and cell phone in a waterproof pouch. 

Having read this cautionary tale www.facebook.com/NorthDevonExplorers/posts/789978681730602
Makes me think that taking a towline is a very good idea.

thank you.

I read that article yes. Probably my worst nightmare to be honest is being swept out to sea.  I have all the essential items on my PFD like you said IF i was to be separated with my boat, it was more the other stuff to carry in my box for things like repairs etc on the fly.

I think i saw little made up boxes online but i cant remember what else was in it.
*Carabiner
*Paddle Leash(for when you may need both hands)
*Reflector patch (although as you said i have HI VIs stickers on my paddle, I wear HI VIS clothing/hat and i even had my ski custom made with a HI VIS tail paint job!)
*Tow line(thanks i agree this would be handy!)
*Emergency steering bungee
*Duct tape.

Right-o.  I think I have it! Thanks a mill guys.  Safe paddling.