Best Sealent for Screws

[Cornishkiwi]

Hi All

Just a curiosity question, doing a deck Refurbishment at the moment with a teak deck onto fibreglass, and will be reputting my mast step back on, stanchion post screws back in, hand rail bolts and other accessories etc soon and was just wondering what’s the best thing to coat the screws:bolts with to keep them water tight before they go back in? I was going to just use silicon, but after a While it does go brittle so was wondering if there was any other suggestions or better products to use??

Thank you