An ink that won't rub off the kayak?

... I'll have to remember which spaghetti piece is which length...

Weld a 4 inch piece, vertically. The second piece 20 inches away, vertically. A third piece at 22 inches, vertically. Three small, permanent vertical lines on the side of your yak. All you need is a 12-inch piece of HDPE welding rod cut into 3rds. Someone that fix’s kayaks has the welding rods and prob wouldn’t charge to weld 3 little lines on a yak.

I just Gooped a platicized flexible sewing measuring tape to the gunwale - its been there for about 10 years. Make sure you clean yak and tape with denatured alcohol before Gooping.  And put the low numbers near you, higher numbers away - I'd always have to do the subtraction because I did the opposite.

I know this would be taking it out of the water, but on the 19 Outback, those 4 black handle, bungie, rail slide, thingie’s are 22 1/4”!

Scotty