I haven't kept fish in a few years. When I did I used a traditional hard-sided cooler. Now that I am kayaking I don't want a bulky cooler. Aren't there some flexible coolers now that can be folded or scrunched up to fit into available space better? Are these things a major pain to clean fish slime out of?

Yes, they are a pain to clean and I don’t use it for fishing.  They have come a long way in keeping stuff cold, but I would line it with a garbage bag if using to fish

I don't find a flexible cooler hard to clean more so than getting one that a fish can't puncher.  One puncher, then the insulation gets nasty and you can't clean that.

 

I use a fish basket and then put the fish in the cooler when I get back.  

 

Yes... I havw come back wet and nasty sometimes because I kept a basket of fish or a stringer full of catfish on my legs as I paddled back.  

Good point about the fins puncturing it. hadn't considered that

HPA makes a 21x12x12 semi-rigid dry storage/livewell for kayaks in satin black with orange graphics. The 'Buy It Now'  is a cool $100 w/free shipping but the same unit usually starts at $50 on auction with the same free shipping.