Dr. Eric "Doc" Strand, Chief Spartan

Hi! If you’re on this page then you got one of my business cards. Let me tell you a bit about myself, and Spartan Scuba.

First off, yes, I am a real doctor. I’ve been in medicine since 2001 practicing Chinese Medicine with an emphasis on injury/sports medicine and women’s health. Before my life in healthcare, however, I served for eight years in the US Marine Corps. I can’t tell you about what I did, or who I worked with, but I speak, read, and write Korean, and I didn’t before the Marines. 

A life-long martial artist I believe that training is everything, and that respect is earned, not given. With that I have built Spartan Scuba around the philosophy that first, the more thorough the training the easier the diving; and second, I and my dive leaders will strive for nothing less than the best for our community of divers. We will earn your respect.

Lastly I will say that as divers it is our responsibility to care for our environment, both above and below. We emphasize being conscientious observers underwater; enjoy the scenery up close and personal, clean up the biproduct of human existence when and where we find it, take only pictures, and leave only bubbles. 

Where it all started.

I didn’t start diving officially until 2016 when a group of my Marine Corps buddies wanted to do a reunion out in Hawaii where most of us met and were stationed together back in the early 90’s. I thought it would be fun to get certified with my family and go actually dive while we were there, and I was right! 

While everyone else in my family decided they were down for diving IF it was in warm, tropical waters, I caught the bug- at least a little. We came back and I went on a few dive runs with the shop I certified with, but then I stopped. No dives in 2017- not one. Then in 2018 after a trip to Canada to visit an old classmate from grades 7/8, who also happened to be an avid diver I was once again enamored with the underwater world. I came back with renewed vigor, and really started cranking out the dives. 

I got involved on a whole new level, and I think my level of excitement for advancing through the ranks to dive leader took everyone aback. Where was I going to find time for all of this on top of running a busy medical clinic? The answer came in the form of Covid. For better or worse, my clinic suddenly required less of my time because there were fewer people out and about. Although we did stay open and taking care of patients throughout the pandemic, I found a silver lining in traffic-less roads and empty dive sites to explore. Talk about heaven!

Dalton's Triangle

Dalton’s Triangle can be used to calculate everything from the best Nitrox mix for a dive, your MOD for a particular gas mix, or even the partial pressure of a gas at a given depth and Nitrox mix. This is one of the most imprtant tools in your dive kit!

Using the triangle above: MOD is simply dividing your desired max Partial Pressure (typically 1.4) by your percent O2 as a decimal: 32% = 0.32, for example. This results in a pressure P of 4.37. Subtract one atmosphere for everything above water = 3.37, then multiply that by the weight of water: 33 for salt water, 34 for fresh. The result?, 111 feet of salt water. 

Remember, always round DOWN your end result for depth!

In order to calculate your best gas mix for a given depth you first need two things: your desired PPO2 (top of the triangle), and your desired P-pressure. Since we don’t talk in terms of pressure, but instead “depth” we need to first convert depth to pressure.

Pressure (P) = (D) depth/33 + 1 (atmosphere above water).

Once we determine our P-pressure, we can plug our numbers back into Dalton’s Triangle and calculate our best gas mix, let’s say for a desired PO2 of 1.5, this time (aka: ‘travel gas’).

Since we are now looking for the bottom right corner of the triangle, FO2, or fraction of O2, our equation would look like this:

FO2 = PO2/P :: FO2 = 1.5/5 :: FO2 = 0.3, or 30%.

You can do it just as easily for a sport dive mix of 1.4 PO2.

FO2 = 1.4/5 = 0.28, or 28% Nitrox!


%N is the percentage of nitrogen in your Nitrox mix. For example, if you are diving 32% Nitrox you have 0.68 N2. Replace %N in the equation with 0.68

D is the depth you dived to, or are planning to dive to.

  • Step 1: divide your %N by 0.79.
  • Step 2: add 33 to your depth. 
  • Step 3: multiply the results of steps 1 and 2.
  • Step 4: subtract 33. This is your Equivalent Air Depth for your Nitrox mix.

bar to psi: psi/14.7 = bar

psi to bar: bar*14.7 = psi

There are two methods of calculating temperature impact on tank pressure. The first is what I call the “cheater” method: 

Cheater T to V: 1°F=5 psi 1C=0.6 bar

In other words, for every degree of Fahrenheit, the tank pressure changes by about 5 psi. Similarly for every degree of Celsius the tank pressure changes about 0.6 bar.

The formula for determining the exact change is:

P based on T∆: psi2 = ((F2+460)*((psi1+14.7)/(F1+460)))-14.7


Metric-Imperial: 3.3 *meters= feet


ImperialMetric: feet/3.3 = meters

Your adventure awaits.

Becoming a SCUBA diver is a fairly simple process. Honestly, the most difficult things you’ll face are where you want to train (cooler, green waters of the PNW – or – crystal clear, warm, blue waters of the tropics), and what color fins and mask you’ll want. After all, diving is, if nothing else, a recreation of fashion!

The first thing you should do is decide when you want to become a diver. Just like the image below says, no one ever wishes they had waited until later in life!

If you click the image above you’ll open a window that will tell you everything you need and we do different where it comes to this initial certification. Once you’ve decided you’re ready, the next important decision is here, or there. Cold water, or warm. They’re both amazing, relaxing, with a plethora of life to experience, but your affinity for one climate or another will make or break your experience: pick the option that suits you best!

That’s really it. Once you sign we will personally guide you through the rest. No large groups or crowds to get lost in: it’s you and your instructional team from start to finish. The only time that may change is during certification dives. All of your training is designed to focus on you alone, or you and your small group!

Better to have and not need than need and not have.

DAN will CYA!

DAN* dive accident insurance offers divers an affordable way to protect themselves against unpredictable expenses associated with diving accidents and dive travel. Plans pay 100% of eligible accident medical expenses up to US $500,000, and some cover nondiving and named water sports accidents as well as diving accidents, up to and even including recompression therapy and search and rescue.

Find out more.

*Spartan Scuba receives no benefit from DAN, nor do we imply any affiliation other than using and recommending their services. 

Let the GI Bill bring your adventure to life!

Did you know that your GI Bill can help pay for some, if not all of your SCUBA dreams to become a reality? It’s true!

Everything from the basic diver all the way up to the top tier of the professional ladder, there is an approved training program which will satisfy your needs. 

Get certified to be a Nitrox diver right out of the gate, or how about becoming a Rescue Diver, complete will all the first aid courses?

Ever thought about being a Divemaster? We’ve got you covered. 

Wanna’ be a tech diver? Come along with Doc on a deep deco dive, switching between multiple gasses on your way out, and let the GI Bill help you get there. 

All of this and more is possible. For more information, click here!

A few of my favorite things...

Favorite place to travel and dive:

Put me down for Cozumel. I love the diving, the food, and the people. I’m also a huge fan of staying at Scuba Club Cozumel. Epic experience!

I love the feeling of getting up just before the sun hits the water, sitting with my coffee under the palapa on the beach, and dreaming about what the day’s adventure will bring. Cozumel has everything a diver could want: boat and shore diving, exceptionally warm waters, drift diving, and terrific sea life! From Spotted Eagle Rays to Black Tip Shark, Spotted Drum Fish to Sea Horses, this place has it all.

Favorite regulator kit:

This is a tough one! I “grew up” on ScubaPro, so I still have a number of these laying around. When I’m just diving one tank, then my primary regulator is a smoked out MK19 in DIN with a black G260. That thing is bullet proof and has a diaphragm the size of a baby’s head! Breathing off that second stage is like tipping our head back and letting the air just slide down into your lungs. 

That being said, all of my stage bottles have either MK25 or AC25 (Cressi) 1st stages with DiveRite XT4 second stages, and my deco O2 bottle is a Hollis, primarily because it’s green and fancy, but also because it breathes SO NICE.

Basically, I love big diaphragms and easy breathing. 

If I had to pick just ONE dive computer...

Again, I was raised on ScubaPro, so for a long time that was the bread and butter of diving. And, while I do dive a HUD (which is a must for diving in the murky, dark waters of the PWN), my all time, hands down favorite personal dive computer (PDC) is the Shearwater Teric. 

This thing really has the trifecta in spades. Ease of use, durability, and fancy AF to look at! Add to that the FREE cloud uploading of your dives and the spectacular people who make and maintain these products (I’m looking at you, DiveTronix!), you simply cannot go wrong with a Teric on your wrist (…and a Perdix on the other wrist).

My favorite course to teach!

I really love teaching all of the specialty courses, but my favorite really has to be Divemaster. To me, this is the epitome of diving. From this point forward you may learn more about how to teach skills, and the legal aspects of running a business, but you’ll never learn anything more about diving! In fact, the higher you go from this point on, any time a course starts to talk about the physics of diving, or what to look for with regards to diver distress, they simply say, “here’s the basics; if you need more information, see chapter XX in the Divemaster course”!

For me, running the Divemaster course is where you really help to make leaders in the field. I get to set the example and then just watch them learn and grow. Such a fantastic feeling as they take their first groups out wearing the big kid fins!