shoddy helmets 4 sale

I recently purchased a NEW kayak saftey helmet on Trade Me garenteed to be up to our NZ white water standard. I was told it was originaly bought and recomended by a reputable Kayak franchise cental North Island suitable for any grade river. On arrival it looked a little dodgy. It has very thick low density padding (sponge) inside of it. Its very comfortable to wear when dry but the sponge holds a lot of water when imersed (takes a long time to dry). Within weeks of this purchase what looks like the same type of helmet was being flogged off on Trade Me by the carton (14 helmets were sold for $51.00). These helmets are aparently designed for rowers (have you ever seen a rower with a helmet) not suitable for high impact. With the warning "use for other watersport at your own risk". DO we not have a NZ standard. Yes you can say why buy a important saftey item from Trade Me However the Trade Me seller claims to have purchased this from a reputable kayak shop for in excess of $100.00 This helmet looks substandard compared to other older models I have.