Underwater Fishing Scout ROV — MVP 1

Undulating Dorsal Fin — Primary Thrust

The seahorse's dorsal fin oscillates at up to 35Hz in nature. We replicate this with a series of servo-driven fin rays running along the dorsal (top) ridge of the body. A sine wave propagates down the array — the frequency controls speed, amplitude controls power, and wave direction controls forward/reverse.

This is genuinely silent propulsion. Traditional thrusters create pressure waves that fish detect through their lateral line from meters away. An undulating fin mimics the movement of actual marine life and produces minimal turbulence. This is arguably the product's biggest competitive advantage over conventional ROVs.

Buoyancy Control

MVP 1: Manual adjustable ballast weights. Velcro-mounted lead/steel weights on the underside. Swap weight amounts when switching salt ↔ fresh. Simple, reliable, no moving parts.

Future: Active buoyancy engine. Small syringe pump in the mid segment — push water into a bladder to sink, push it out to rise. Automated depth hold. Auto-compensates for salt vs fresh density difference (~2.5% buoyancy shift).

Prehensile Tail — Zero-Power Station Keeping

The seahorse's tail is its anchor. It wraps around coral, seaweed, or structure and holds position with zero energy expenditure. We replicate this with a tendon-driven curling mechanism — one servo, two cables, and the segmented tail curls like the real thing.

This solves the biggest energy problem in patrol mode: holding position in current. Instead of burning battery fighting drift, the tail grips structure and the entire propulsion system shuts down. Combined with energy harvesting, the ROV can potentially run energy-positive in patrol mode — harvesting more than it consumes.

MVP 1 — Validation BOM Strategy

Phase 1 focuses on validating stereo underwater vision. Waterproofing is minimal — acrylic tube or dry bag enclosure. No custom PCB. Off-the-shelf components on a dev platform. Get it in the water fast, prove the cameras work, iterate from there.

Why This Stack?

The Raspberry Pi 5 gives us dual CSI-2 for synchronized stereo capture, enough compute for real-time depth mapping and VR streaming, and a full Linux stack for rapid iteration. No custom PCB needed for validation.

Side-mounted fisheye cameras mimic real seahorse eye placement. Each eye sits in a socket on the side of the head with a dome viewport housing a 190°+ fisheye lens. The wide FOV captures a VR180 stereo panorama — the user puts on a headset and is underwater, looking around freely through the seahorse's eyes. Meanwhile, the depth pipeline dewarps the central stereo region and computes disparity maps for structure identification. Dual pipeline: immersive VR experience + computed depth data. Based on PiCam360's VR streaming approach with 1/50× bandwidth compression.

The tether-first approach eliminates the hardest underwater problem — wireless comms. RF dies in water, acoustic is slow, optical is line-of-sight. A thin cable gives us full-bandwidth video + bidirectional control with zero latency. The tether runs through the spine channel, protected by the segmented body.

Undulating fin propulsion is silent and low-turbidity. Fish detect traditional thrusters through their lateral line organ from meters away. A wave-driven fin mimics natural fish movement and won't spook your targets.

Software Stack

Underwater Vision Challenges

Dual Water Design Considerations

Freshwater: Lower density (~1.0 g/cm³). ROV will be less buoyant — may need less ballast weight. No corrosion concern on most materials. Better visibility in lakes, worse in rivers with sediment.

Saltwater: Higher density (~1.025 g/cm³). More buoyant — add ballast to compensate. Corrosion on anything non-marine-grade. Use 316 SS or titanium fasteners, conformal coat all electronics, rinse after every use. Better visibility nearshore in calm conditions.

Ballast strategy: Adjustable ballast weights with Velcro mount for MVP 1. Swap weights when switching between salt and fresh. Future: active buoyancy engine (syringe pump) auto-compensates.

Biomimetic Armor — Seahorse Plate Structure

Inspired by McKittrick & Meyers' research at UC San Diego. The seahorse tail uses 36 square segments, each made of 4 L-shaped interlocking plates. The structure compresses to ~50% before permanent damage, protecting the spine. We apply the same principles to create a modular, impact-resistant, field-replaceable enclosure for the ROV electronics.

Ref: UCSD — Seahorse Armor Research · Acta Biomaterialia, 2013

Bio → ROV Mapping

Electronics Placement by Zone

Material Selection — Dual Water Rated

Form Factor Advantage — Fishing Stealth

The seahorse shape isn't cosmetic — it's functional camouflage. Side-mounted eyes are the key detail. Fish have evolved to recognize eye placement as friend-or-foe. Forward-facing eyes (cats, sharks, eagles) signal predator. Side-facing eyes (most fish, seahorses, herbivores) signal non-threat. By placing cameras on the sides of the head like a real seahorse, the ROV registers as fauna, not hunter. It gets closer to fish without triggering flight response — exactly what you need for a scouting tool.

The compact profile also means no protruding motor arms to snag on weeds, branches, or fishing line — common hazards in the exact structures where fish hold. The dome viewports for the fisheye lenses sit flush in the curved eye sockets — smooth hydrodynamic profile with minimal drag.

The Endurance Equation

The combination of prehensile tail anchoring, solar harvesting, and water turbine generation fundamentally changes what this device is. It's not an ROV you use for 20 minutes. It's an autonomous underwater observation platform that can run for hours — potentially all day in the right conditions.

The key insight: anchored patrol mode draws dramatically less power than swimming. Propulsion is 60-70% of total energy budget. Eliminate it and you extend runtime 3-4x from battery alone. Add harvesting on top and the math gets very interesting.

All-Day Patrol Scenario

6:00 AM — Deploy seahorse at a channel swing on a river. Thruster transit to submerged log jam 40m upstream. Tail anchors to a branch on the current-facing side.

6:05 AM–12:00 PM — Anchored patrol mode. Cameras at low frame rate duty cycle. Solar charging from morning sun. Turbine harvesting from river current. Logging water temp, depth, and video frames. When fish activity detected, switches to full-rate video and flags timestamp.

12:00 PM — Retrieve. You have 6 hours of data: fish activity heatmap (most active 7:15–8:30 AM), water temp curve (peaked at 18.2°C at 10 AM), and video clips of every fish that passed the structure. You now know exactly when and where to fish tomorrow.

No fish finder on the market provides this dataset.

Phase 1 — Fisheye Stereo Vision + VR Streaming

WE ARE HERE

Phase 2 — Propulsion + Tail Validation

Phase 3 — Seahorse Body + Energy Harvesting

Phase 4 — Product

Future — Autonomy