How do you subtly hint your partner about kinks

I’m 25 M and I have a partner 23M. He knows I’m kinky and vaguely knows what I would like to try.

I have suggested/hinted to some kink stuff in the past and has brushed it off a bit (not uncomfortable with it, I asked, i think he is just “scared” for a lack of a better word)

I of course give him time to feel how he actually fells about it but I don’t want to ask him again I case he then fells forced.

How do I subtly give him hints to make him think about what he is comfortable with trying?

This kink stuff im into is varied, light pup play, power exange, voyeurism, water sports, and three somes/partner swap.

To note. He actually engaged in water sports himself once when he was a little drunk(I didn’t bring it up myself).

I know somebody is probably gonna say just ask him, but my bf is a pleaser, if ask something of him multiple times he is gonna do it for me, and I don’t want that I want him to do it because he is comfortable with it.

I would love some insight into how to deal with the situation.

Btw we been together 4 years, and he has once actually suggested a threesome (didn’t end up happening because of the guy).

Soo so far he got watersports and one foot into threesome.