Need to replace my dock lines and fender lines; best material?

[chasfgr]

3-strand nylon for dock lines, unless you're on inland waters - you need the stretch, but don't go too large diameteror you lose it again.
Watch out for wet laid nylon springs heating up and losing tensile strength. Eqally don't go so oversize that your teeth jar abunk, as each spring stops stretching.
For fenders I use sections of old worn dock line - and I never use my safety rails, always back to cabin-top handholds. I've seen too many capsized supports.

[Paul54]

I tend to keep a candle on board. I use it mostly for lines and heat shrink. Also it is a good emergency light source and very romantic.