Both run alongside the mothership. Both extend what the main yacht can do. The similarity ends there. A chase boat is a fast day platform. A shadow vessel is a slow logistics yacht that carries vehicles, helicopters, submarines, and toys. Owners who confuse the two end up specifying the wrong hull, and that mistake is expensive to unwind. This page sets out the distinction for fleet planners and project managers.
A parallel comparison from the support-vessel angle lives at support yacht vs chase boat.
Two different problems
The chase boat exists to extend the mothership's day. Sport-fishing, dive ops, beach runs, fast crew transfers, charter overflow. It runs at 30 to 40 knots cruise, carries 12 to 20 day guests, and lives in a normal marina berth.
The shadow vessel exists to extend the mothership's payload. Containerised toys, vehicles, helicopter, submarine, additional crew accommodation, dive compressor station, fuel bunker. It runs at 12 to 16 knots, displaces 800 to 3,000 tonnes, and needs commercial berthing or anchor space.
You buy a chase boat when the mothership is too slow. You buy a shadow vessel when the mothership is too small.
Side-by-side specification
| Parameter | Chase boat | Shadow vessel |
|---|---|---|
| Length | 10 to 20 m | 30 to 70 m |
| Displacement | 8 to 35 t | 800 to 3,000 t |
| Cruise speed | 30 to 40 kn | 12 to 16 kn |
| Range | 400 to 850 nm | 4,000 to 7,000 nm |
| Crew | 1 to 4 | 8 to 22 |
| Toy capacity | Day kit only | Helicopter, submarine, vehicles, multiple tenders |
| Classification | MCA coded or RCD | Commercial cargo, often Bureau Veritas or Lloyd's |
| Stowed within mothership | Never | Never |
| Typical new-build cost | 600 k to 7 m euros | 25 m to 90 m euros |
| Build slot lead time | 12 to 24 months | 36 to 60 months |
| Berthing | Standard marina | Commercial dock or AP |
| Operates ahead of mothership | Often | Sometimes |
| Operates independently of mothership | Day trips only | Multi-week deliveries |
Where each one wins
A chase boat wins when the day programme demands speed. Sport-fishing tournaments, dive site hopping, fast island runs, charter principal day-tripping while guests stay on the mothership. The decision usually surfaces once a programme realises the tender garage cannot accommodate a hull big enough to do the job. We cover the use-case detail at sport-fishing chase boats, expedition chase boats, and the chase-boat use-cases library.
A shadow vessel wins when the mothership cannot carry the payload. The classic test: if the brief includes a helicopter that needs more than touch-and-go, a manned submarine, or more than three serious tenders, the math points to a shadow. Builders specialising in this segment include Damen Yachting (the SeaXplorer line), Astilleros Armon, Lurssen, and Pendennis. We cover them at shadow vessel builders, helicopter support vessels, and submarine support vessels.
They are not substitutes
The most common planning error is treating these as alternatives at a single budget line. They are not. They serve different jobs, and the largest programmes carry both.
A 70 metre yacht with a serious dive and sport-fishing brief might carry: one 9 metre limousine tender in the garage, one 7 metre SOLAS rescue tender, one 15 metre chase boat at independent berth, and a 55 metre shadow vessel carrying the dive station, the helicopter, the spare RIB, and three jet-skis. That is four hulls, four crews, four maintenance contracts. That is also the only configuration that delivers the programme.
The wrong configurations we see most often:
- A shadow vessel ordered when the real need was a chase boat. The shadow ends up underused because the mothership never travels far enough to need the payload.
- A chase boat ordered when the real need was a shadow vessel. The owner discovers at season two that the chase cannot carry the helicopter, the submarine, or the dive compressor, and the mothership's aft deck is still cluttered.
Operating economics
Chase-boat running costs sit roughly at 8 to 15 per cent of acquisition annually, all-in. Crew, berth, fuel, insurance, refits, surveys. We unpack the model at chase boat cost.
Shadow-vessel running costs sit at 8 to 12 per cent of acquisition, but on a number an order of magnitude larger. A 50 metre shadow at 35 million euros all-in delivered is a 3 to 4 million euro per year operating commitment. Crew alone runs 1.2 to 1.8 million annually for the right team. Berth costs in Monaco or Antibes during high season are commercial-rate, not yacht-rate.
Decision flow for project managers
Use this sequence.
- Define the day programme. What does the principal want to do at speed?
- Define the deep brief. Is there a helicopter, a submarine, a manned dive operation, or a vehicle programme?
- Map both against the mothership's garage capacity, aft-deck layout, and helideck rating.
- If the day programme breaks the garage, specify a chase boat.
- If the deep brief breaks the helideck or the toy stowage, specify a shadow vessel.
- If both break, specify both.
The path back to the broader trade is at the chase-boats pillar and the support-vessels pillar. Brokerage stock for both segments lives at /brokerage/for-sale/.