A good quality silicon rubber watch strap featuring a criss-cross pattern along its length

Available  only in navy blue to fit 20mm lugs it features a side opening 3 fold clasp with a secure over-lock tab.
Being high grade silicon rubber it is of course totally impervious to water

With a small amount of adjustment available on the clasp it is 18.5 cms at its longest
By cutting segments from the clasp end of the strap it can be reduced in length by up to 6 cms
Just add the size of your watch case to compare to your wrist size