Marine is the application where rope choice has real consequences — and where the three-way choice between nylon, PP and polyester is easiest to reason about, because each fiber owns a distinct job.
Choose by line function
Anchor lines → nylon. Anchoring is a shock-load problem: waves snatch at the boat and the line must absorb it. Nylon 3-strand twisted is the classic answer — elastic, spliceable, and it sinks, which helps the anchor set. Sizing follows boat length, displacement and windage: give the supplier vessel details, not just a diameter.
Dock lines → nylon, double braid for premium. Dock lines are handled daily and take cyclic surge loads. Nylon double braided is supple, strong and kind to cleats and hands; pre-spliced eyes to your cleat size make them shelf-ready.
Mooring lines (boats & ships) → nylon for elasticity, PP 8-strand for floating economy. PP multifilament 8-strand plaited is the workhorse of commercial mooring: floating, torque-free, economical in 24–80 mm. Where energy absorption is critical, nylon 8-strand or double braid steps in.
Utility & floating lines → PP. Buoy lines, water-ski lines, swim barriers and general deck utility: PP hollow braid floats and splices in minutes.
Halyards & position-holding rigging → polyester. Where the line must not stretch and lives in the sun for years: polyester, twisted or solid braid. See also the outdoor/UV guide.
The mooring RFQ done right
Commercial mooring is specified, not shopped. A complete RFQ states: vessel type and size · line function and arrangement · required minimum breaking load (from your standard or class rule, if applicable) · diameter range · finished length (cut length vs spliced assembly) · eye splice size and thimble type · quantity · destination port · required documentation. Half of these are missing in most first emails — each omission is one extra email round-trip.
Also read: which ropes float · rope materials comparison · how to specify rope for an RFQ.
Safety note: mooring design for commercial vessels is an engineering decision under class/flag rules. Product pages here give typical ranges only — project specifications and certified test data are confirmed per quotation.