Est. 2009 · USCG certified · Mission Bay, CA
Onboard nitrox, blended while you gear up
The only San Diego dive charter that blends nitrox on site. Anything from 22% to 40%, usually around 32%, single tank or doubles, mixed for the dive in front of you.
How the gas works on the Marissa
Blended on the boat, not trucked in
Continuous-blending nitrox on board, single tank or doubles. The only San Diego charter with fills on site, which means the mix is made for the dive you are about to do rather than whatever the shop had in the rack yesterday.
Anything from 22% to 40%
Usually around 32%. Bring your own analyser. The crew analyses every fill as it comes off the compressor, but that check is ours, and the number you dive on should come from your own equipment. Analyse your tank and sign for it the way you would on any boat.
High-pressure fills
A high-pressure compressor fills to 4200 psi, so HP steel tanks are straightforward rather than a favour. AL80s with DIN or Yoke valves and air fills come with every ticket.
Paid on the boat
Nitrox is an add-on rather than a package. Singles are $16 a fill and doubles $28, payable on board, so you are not buying gas you turn out not to need.
Nitrox certification required
Enriched-air fills go to nitrox-certified divers. If you are not certified yet, dive air with us and come back on the mix. Air fills are included either way.
Where the mix actually helps
Wreck Alley sits at 65 to 105 feet and the second dive of the day is where nitrox earns its keep. Trimix and other helium mixes are not blended on board and come pre-blended, as on any day boat.
Why it matters on a day boat
Most San Diego charters send you to a shop the night before, which means guessing your mix before you know the conditions, then diving whatever you guessed. Fills on site move that decision to the dock, after the crew has looked at the water and after you know which sites the day is actually going to allow.
It matters most on the second dive. A 65 to 105 foot wreck followed by a surface interval and a second drop is the profile where a richer mix buys back bottom time, and it is the profile the Marissa runs most days.
What is included either way: AL80 tanks with DIN or Yoke valves, air fills on board, and weights. Nitrox is the add-on, for nitrox-certified divers, paid on the boat.
Oxygen-clean tanks, and checking your own gas
You do not need an oxygen-clean tank for nitrox on the Marissa. Standard mixes of 40% or less go into the same tank you would dive on air, whether that is one of our AL80s or a tank you bring, as long as your tank’s hydrostatic test and visual inspection are both current.
We blend continuously, which means the oxygen is mixed into the air before it reaches the compressor and your tank is filled with the finished mix. That is why a regular tank is fine at these mixes, and it is also why our system is, “technically,” not oxygen clean. We would rather you hear that from us before you fill.
Every diver checks their own tank on every fill, with their own analyser. The crew analyses every fill as well, but rely on your own equipment for the number you dive. When you sign for your gas you are confirming the percentage yourself, and you are agreeing that checking it is your responsibility and that you understand and accept the risk of diving it.
If something does not look right, say so on deck. If your tank reads 21% when you asked for 32%, it was filled with air by mistake, and the crew would much rather hear about it before the dive than after it. We can fix it, but not if we don’t know.
Nitrox questions divers ask
Which San Diego dive boat has nitrox on board?
The Marissa. Nitrox is blended on board from 22% to 40%, usually around 32%, and it is the only San Diego charter with fills on site.
Do you have nitrox? What mix?
Yes. Marissa blends nitrox on board from 22% to 40%, usually around 32%. Bring your own analyzer. The crew analyzes every fill, but the reading you dive on should come from your own equipment.
What does nitrox cost?
Nitrox is available for nitrox-certified divers. $16 per fill for singles and $28 for doubles. We can run your card for it right on the boat.
Do I need an oxygen-clean tank for nitrox?
No, not for standard mixes of 40% or less. Our nitrox is continuously blended, so the oxygen goes into the air before the compressor and your tank is filled with the finished mix. That also means our system is, technically, not oxygen clean. A tank you bring needs a current hydrostatic test and visual inspection.
Who checks my nitrox mix?
You do, on every fill, with your own analyser. The crew analyses each fill too, but your own reading is the one to rely on. Signing for your gas means you have checked the percentage yourself and accept the risk of diving it. If the number looks wrong, tell the crew. We can fix it, but only if we know.
Can you fill high-pressure steel tanks?
Yes. A high-pressure compressor on board fills to 4200 psi.
Do you blend trimix on board?
No. Trimix is not blended on board. Helium-based mixes come pre-blended, as on any day boat, and deco and bailout bottles should arrive already filled.
What gas can you provide for a tech dive?
Marissa can provide air and nitrox on board. Divers should bring deco, trimix, and bailout bottles already blended and coordinate gas needs ahead of time.
Where to dive it
Nitrox is available on every trip we run. Wreck diving is where most divers want it, tech days add staged bottles on top of it, and the Coronado Islands run three to four dives across a full day, which is the longest gas day on the schedule.
Book a trip and add nitrox
Pick a trip and tell the crew your mix. If you would rather talk gas through first, reach Captain Lora directly.