Yep get a seat sorted to sit them inside the boat.
I have something like this....
https://www.compactwatercraft.co.uk/...-for-riverstar (give site a few moments to load its slow for me)
Mine came with one of our used boats. I guess it's about 15yrs old and the material is far thicker and nicer to sit on than cheap li-lo type pvc. It is pretty well full width in an Aerotec but would not be so in a broad Honwave like yours.
It has tabs so you can tie the backrest to the existing seat making a mini sofa.
Mrs F loves the idea of travelling sitting on that but two issues... she would take up too much floor space... and it's pink so I've banned it.