{"id":117435,"date":"2026-10-03T18:47:37","date_gmt":"2026-10-03T14:47:37","guid":{"rendered":"https:\/\/www.oxsea.com\/mini-scuba-tank-for-boats\/"},"modified":"2026-10-03T18:47:37","modified_gmt":"2026-10-03T14:47:37","slug":"mini-scuba-tank-for-boats","status":"publish","type":"page","link":"https:\/\/www.oxsea.com\/en\/mini-scuba-tank-for-boats\/","title":{"rendered":"Mini scuba tank for boats: a practical guide for boat owners"},"content":{"rendered":"

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Mini scuba tank for boats: a practical guide for boat owners<\/h1>\n

A line caught in the propeller just as you head back to port. An anchor that will not come up. Keys slipping overboard at anchor. At moments like these, someone has to look under the hull. Holding your breath, you often end up making a series of short dives, working almost blind. With a mini scuba tank on board, you can stay down for a few minutes with your eyes on the problem.<\/p>\n

This guide helps you choose a model to suit your boat’s equipment, organise refills on board and do the job without taking needless risks. The full range is in our mini scuba tank shop<\/a>.<\/p>\n

What a mini scuba tank can fix under the hull<\/h2>\n

A rope round the propeller.<\/strong> A fender line, the line from a lobster pot, a scrap of net: once it has wrapped itself round the shaft or the drive leg, you can rarely cut it free on a single breath. With air, you cut it turn by turn, then check that nothing is left.<\/p>\n

A stuck anchor.<\/strong> If the anchorage is shallow, you follow the chain down and free the anchor by hand. If it is caught below the shallow zone where you can safely work, do not push your luck.<\/p>\n

Checking the hull.<\/strong> After touching bottom, before a passage or to judge the state of the antifouling: hull, keel, rudder, propeller. You can also see whether the anode will last until the next haul-out.<\/p>\n

Something dropped overboard.<\/strong> Phone, keys, winch handle: in shallow, clear water, you can often get them back in a few minutes.<\/p>\n

Which model for your boat<\/h2>\n

The first question to ask yourself: do you have a 12 V battery on board? It decides how you will refill, and so which model you need.<\/p>\n

No power on board<\/strong> (tender, small sailing boat or RIB without a battery). Go for the OX500 tank<\/a> (\u20ac199.99) with the manual pump<\/a> (\u20ac159.99), which works without electricity. You hold the OX500 in your mouth with its silicone mouthpiece, its built-in gauge shows how much air is left, and it weighs less than 1 kg underwater. The two also come as a pack, at \u20ac359.99.<\/p>\n

A 12 V battery on board.<\/strong> The 12 V mini compressor<\/a> (\u20ac549.99) runs off the boat’s battery, or on 220 V shore power in port. It refills faster than the pump and is the better choice if you have several jobs to do in one day.<\/p>\n

You need both hands.<\/strong> The OX500Plus<\/a> (\u20ac289.99) holds as much air as the OX500 (0.5 L, up to 8 minutes) but can also be worn on your back, with a harness and an external regulator. Your hands stay free to hold the shaft and cut. An external pressure gauge is included.<\/p>\n

Longer jobs.<\/strong> The OX1000<\/a> (\u20ac299.99) holds 1 L of air, about 15 minutes, and is worn on your back with harness and external regulator. Note that the manual pump cannot refill it. You need the mini compressor or a transfer station connected to a full-size scuba tank. The OX1000 + mini compressor pack costs \u20ac849.99.<\/p>\n

To compare the three models point by point, see our mini scuba tank comparison<\/a>.<\/p>\n

\n\n\n\n\n\n\n\n\n\n
Situation<\/th>\nRecommended model<\/th>\nRefill<\/th>\n<\/tr>\n<\/thead>\n
Quick check or dropped item, boat without a battery<\/td>\nOX500<\/td>\nManual pump, about 20 min<\/td>\n<\/tr>\n
Rope or net in the propeller, both hands needed<\/td>\nOX500Plus worn on your back<\/td>\nManual pump (about 20 min) or 12 V mini compressor (about 12 min)<\/td>\n<\/tr>\n
Several jobs in a day, 12 V battery on board<\/td>\nOX500 or OX500Plus<\/td>\n12 V mini compressor, about 12 min<\/td>\n<\/tr>\n
Full hull inspection, anode check<\/td>\nOX1000<\/td>\n12 V mini compressor (about 20 min) or transfer station (about 1 min)<\/td>\n<\/tr>\n
Scuba tank already on board<\/td>\nAll three models<\/td>\nDIN or yoke transfer station<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

How much time to plan for underwater<\/h2>\n

The stated air times are maximums: up to 8 minutes for 0.5 L, about 15 minutes for 1 L, breathing calmly. Cutting a tight rope or pulling on an anchor makes you breathe faster, and the tank empties sooner.<\/p>\n

So plan the job on the surface: knife tied to your wrist, spot located from the deck, everyone on board clear about their role. Check the gauge before you go down, then regularly. Come up while there is still air left, not on your last breath.<\/p>\n

A very tight rope may take two or three dives. In that case, allow time to refill between each one.<\/p>\n

Refilling on board<\/h2>\n

With the manual pump.<\/strong> It sets up quickly on deck, on the quay or ashore, with no electricity. Allow about 20 minutes of pumping for a 0.5 L tank.<\/p>\n

With the mini compressor.<\/strong> It runs on a 12 V battery or 220 V mains power. Allow about 12 minutes for 0.5 L and about 20 minutes for 1 L. Set it up in the open air, away from the engine exhaust or a generator: a study published by INRS, the French occupational health and safety institute, lists the exhaust from combustion engines among the possible sources of carbon monoxide in compressed air.<\/p>\n

From a full-size scuba tank.<\/strong> A DIN or yoke transfer station refills all three models. For the OX1000, allow about 1 minute.<\/p>\n

OXSEA mini dive tanks are shipped empty, with no air inside. Do a first fill and a test run in port, before you need the tank at sea. Assembly and filling are explained in the video tutorials at OXSEA School<\/a>.<\/p>\n

Where to stow the tank on board<\/h2>\n

After each use at sea, rinse the tank in fresh water, then stow it away from knocks and heat, as our product pages advise. On a boat, that means a locker or a cubby, wedged so it cannot roll when the boat heels, and never in full sun on deck.<\/p>\n

Keep it within reach. A rope in the propeller rarely comes at a good time, and a tank buried under the sail bags costs you time. Keep your mask, knife and tank together.<\/p>\n

Safety: before you go under the hull<\/h2>\n

Engine off.<\/strong> Switch the engine off before you get in the water, and agree that nobody restarts it until you are back on board. DAN Europe, an assistance network specialising in diving, advises checking that no diver is near or under the boat before you start the engine. In an accident reported by Alert Diver, DAN Europe’s magazine, the engine was in neutral while the divers entered the water, then the gear was engaged and a diver was struck by the propeller. An engine in neutral does not protect you: switch it off.<\/p>\n

Never alone.<\/strong> The basic rule of diving applies: never dive alone. Go with a buddy of similar experience, each of you keeping an eye on the other. Under the hull, also keep someone on board: they know what you are doing and for how long, they make sure nobody touches the engine and they can raise the alarm. At sea, VHF channel 16 remains the priority channel for reaching the coastguard. By phone, call 112, the European emergency number, or your local emergency number.<\/p>\n

Alpha flag up.<\/strong> Fly the blue and white Alpha flag from the International Code of Signals while a diver is in the water. The International Regulations for Preventing Collisions at Sea (Rule 27) also cover boats under 12 metres engaged in diving operations. Some areas have their own rules on dive flags: check what applies where you sail.<\/p>\n

Stay close to the hull.<\/strong> You are working under your boat, not around it. Check the current before you go down and, if there is any, hold on to a line tied to the boat. Divers caught in a current do sometimes drift off and cannot get back to shore.<\/p>\n

Never hold your breath on the way up.<\/strong> You are breathing compressed air. DAN points out that lung overexpansion injury can happen even in a shallow swimming pool if you hold your breath while coming up. Breathe normally and continuously, especially near the surface.<\/p>\n

Stay shallow.<\/strong> Hull work is done near the surface. If the problem is deeper down, give up or call in a professional.<\/p>\n

Get trained.<\/strong> Diving is something you learn: go to a dive centre with qualified instructors. Also check with a doctor that you have no medical contraindication.<\/p>\n

Frequently asked questions<\/h2>\n

Can I refill a mini scuba tank with no power on board?<\/h3>\n

Yes, with the manual pump: about 20 minutes for a 0.5 L tank (OX500 or OX500Plus). The 1 L OX1000 is not compatible with the pump. It refills with the mini compressor or from a full-size scuba tank with a transfer station.<\/p>\n

How long can I stay under the hull?<\/h3>\n

Up to 8 minutes with a 0.5 L tank, about 15 minutes with the OX1000. These times drop as soon as you exert yourself. Watch the gauge and come up with air to spare.<\/p>\n

OX500 or OX500Plus for a boat?<\/h3>\n

You hold the OX500 in your mouth: it is the simplest option for a quick check or for retrieving something. The OX500Plus gives you the same air time but can also be worn on your back, which frees your hands to clear a propeller.<\/p>\n

Do I need training to use a mini scuba tank?<\/h3>\n

Training is recommended. We advise learning at a dive centre with qualified instructors. Our video tutorials show you how to handle and refill the equipment, but they do not replace a supervised introduction.<\/p>\n<\/div>\n

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