"Inflatable Kayak" includes an enormous range of products and prices. There's also packrafts as madpom said.
I wouldn't go for a $20 one from The Warehouse. There are thousand dollar + ones with some frame structure that makes them more rigid, presumably more capable on the water and heavier and harder to get set up.
I had a Sevylor Tahiti for a while, paddled around north eastern Germany (Meclenberg) with my daughter and camping gear for a couple of weeks. It wasn't too bad for seaworthiness, though I wouldn't try to paddle one around Stewart Island.
[Audrey Sutherland](https://www.nytimes.com/2020/03/06/obituaries/audrey-sutherland-overlooked.html) did some big trips (more than 8000 miles) in Alaska and BC in one, for exactly the reasons you mention above - she was lightweight/not strong enough to carry a heavy rigid kayak up and down a beach.
I'd consider something similar to start, perhaps something like one of these https://www.mightyape.co.nz/product/komodo-kx2-inflatable-kayak/34654185?gclid=EAIaIQobChMI3-LB99Pm7wIVRauWCh0kQglXEAQYAiABEgI12_D_BwE
It's hard to tell quality looking at the picture, but probably it would hold up for quite a while with reasonable care.
It's not going to last forever, but should give you some fun for shortish paddles off the beach.
Just editing to add: The big problem with these kinds of kayaks (and this price range) is it's hard to see in advance what quality you're getting for your money. The Sevylor I had was good for what it was (11kg, $300), lasted long enough for the kinds of things I was doing with it. The one I linked to above looks similar but it's hard to be sure how it would hold up.
I'm also not sure on the plusses/minuses of this style of kayak vs a packraft. Definitely a decent packraft will be much lighter, well constructed and made of much more durable materials (and cost a lot more), but I'm not sure how they compare in A-B and adverse conditions performance.