There's seakings and storms.

I mean... Rayleigh might swim it, or some of the giants. But Silvers is kind of... a special case. He makes Shanks look like a two-bit poser.

[Making Silvers one of the very very few people in the world Marco might consider stronger than himself.]

Plus he kind of fails at steering ships. So it's that or get stuck on Sabaody all the time.