Only 1% of the Earth is covered in freshwater and 71% is covered in seawater, so it’s not surprising that most divers dive in marine (saltwater) environments. However, people who live in a landlocked state or country may be limited to only freshwater diving since they have no other alternative.
That’s not to say that freshwater diving is worse; some even find freshwater diving more rewarding than saltwater diving. With that said, there are some differences between the two that divers should know if they plan on switching from saltwater diving to freshwater and vice versa. In this article, we will be taking a look at freshwater vs. saltwater diving to see how much each one can impact you.
Dive Type
While the marine environment is perceived as more exciting, sometimes the weather conditions are not always favorable. Generally saltwater dives are done from a boat, so thorough research needs to be done to ensure that it is safe to dive on a particular day. It may take a few hours of travel, or even days in the case of liveaboards, to reach the ideal diving spot.
On the other hand, most freshwater dives are done from the shore, meaning it takes no time at all to start diving. There are no tidal differences and rarely any currents in freshwater bodies, so these factors are seldom issues. Freshwater divers need to prepare for stony bottoms by wearing dive booties.
Altitude
The standard reference for elevation is sea level, so it’s no surprise that oceans and seas are at 0 altitude. Bodies of freshwater, however, can be found at different altitudes. In fact, some lakes are found at very high altitudes, which means that the atmospheric pressure is lower than bodies of water at sea level.
This increases the risk of decompression sickness because surfacing from a dive at high altitudes causes a greater relative reduction in pressure. As a result, altitude diving has shorter no-decompression times and different stop depths using the same dive profile when compared to diving at sea level.
Buoyancy
An object’s buoyancy determines whether it will sink or float in water. Any person or object will be more buoyant in saltwater than freshwater. This is because saltwater is 2.5% denser than freshwater, meaning it is easier to float in saltwater. Divers need more dive weights to achieve neutral buoyancy in saltwater. The exact amount of weight needed depends on their body mass and the type of tank they carry.
You can also think of saltwater also as being heavier than freshwater because of the extra weight that the sodium chloride adds. When saltwater and freshwater mix, such as when a river flows out to sea, then the freshwater will float above the saltwater.
Next, the salinity of saltwater bodies can vary around the world. The dead sea is famously ten times saltier than ordinary seawater for instance. Another factor which affects buoyancy is temperature. Divers may notice that cold water is more negatively buoyant, so less dive weights are needed.
There are several factors which can affect buoyancy, and water salinity is a major one. In order to determine proper weighting, divers will need to perform a buoyancy test when switching between saltwater and freshwater diving or whenever they switch their gear. A general rule of thumb is to double the amount of dive weights used when moving from freshwater to saltwater, or lessen it by half when moving from saltwater to freshwater.
Visibility
The visibility is typically worse diving in freshwater compared to saltwater. Even though saltwater dives have a sandy bottom that can impair visibility when disturbed, it is still clearer compared to freshwater dives.
When diving in lakes, for instance, the bottom is covered in mud which can impact visibility to a greater degree than sand when disturbed. Additionally, freshwater has fewer currents and therefore more static particles. As such, when diving in freshwater, divers need to take extra care not to disturb the bottom when kicking their fins.
Currents
Saltwater diving is greatly affected by the weather conditions. There will be more currents which can make diving challenging and unpredictable.
On the other hand, rivers have a predictable one-way flow, and freshwater currents are generally caused by wind or bottom formations. Isolated freshwater bodies such as lakes are unexposed to tides (except for large lakes) and water movements, so the water is completely still.
Aquatic Life
One of the biggest differences between saltwater and freshwater diving is in the aquatic life that can be found. For the most part, saltwater has more animal diversity than freshwater. Freshwater not only has fewer species, but they are less vibrant and often smaller than their saltwater counterparts. The marine creatures in saltwater tend to be friendlier and curious of divers, though that doesn’t mean you should try to touch them. There are more venomous animals in saltwater, so the risk of a deadly encounter is higher.
When diving in freshwater, one must be careful not to affect the biosecurity of the different bodies of water. Invasive species can be spread from one freshwater body to another through recreational diving. When a species is introduced to an ecosystem where it has no natural predators, it can be detrimental to the whole ecosystem. As such, decontamination of gear is essential not just for maintaining your gear, but the biosecurity of the environment.
Gear Maintenance
Whether you dive in saltwater or freshwater, divers should endeavor to properly clean and store their gear after a dive. Diving in saltwater requires even more care because saltwater, specifically the salt in it, is one of the biggest dangers to your scuba gear.
As soon as the water starts to evaporate, salt crystals will be left behind. When accumulated, they can jam your zippers, valves, or regulator, and they can be sharp enough to puncture your gear. Salt is also an irritant that can cause itchiness and rashes on your skin.
Now, you may think that freshwater requires less maintenance than saltwater, but you’d be mistaken. Saltwater has its own ways of damaging your gear. You should still thoroughly scrub your gear with water and soap to get rid of any invasive micro-species, such as Zebra mussels and Crayfish plague, that can attach to wet gear.
Freshwater Diving Advantages
If you’ve never dived in freshwater before, then it is a great opportunity to see an entirely new aquatic ecosystem. When comparing saltwater and freshwater ecosystems, it’s like you’re on a different planet.
Saltwater environments have the advantage of a larger variety of underwater plants and animals. Freshwater environments have fewer, however they have more unique plants and animals. For instance, you can find 41% of fish species only in freshwater. If you want to explore new and unique ecosystems that simply cannot be found in saltwater, give freshwater diving a shot.
When living in a landlocked state or country, it may be more convenient for you to access bodies of freshwater than saltwater. Those living in the Central United States, for example, may have to drive for an entire day (or go on vacation) to reach the coast. If there’s a near lake, however, then you can just head there instead.
The lack of currents and calmness of freshwater can give divers peace of mind. They don’t have to worry too much about the weather conditions or currents. While riptides can occur in freshwater, the likelihood is significantly lower.
Freshwater Diving Disadvantages
Unfortunately, diving in freshwater is not all rainbows and sunshine. There are a few downsides which may or may not be deal breakers to you. Saltwater divers are almost always surprised at how much colder diving in freshwater is. They’ll check the outdoor temperature, see that it’s pretty warm, and head into the water only to end up shivering. What’s going on here?
The reason why freshwater is colder than saltwater has to do with the salinity of the water as well as how dense it is. The presence of salt in saltwater makes it denser which helps with buoyancy but also retains heat for longer. Freshwater, on the other hand, will feel colder than saltwater even if the temperature outside is the same. Many divers find this change to be uncomfortable, especially if they did not come with the appropriate gear.
Additionally, visibility is often an issue in freshwater environments. Due to how still bodies of freshwater are, they often have lingering particulate matter floating around that can restrict your visibility. Kicking up dirt and debris in freshwater can basically blind you, and this is less of an issue in saltwater. You can try to alleviate this by wearing a high-quality dive mask and taking care not to kick your fins too close to the bottom.
As we discussed above, freshwater environments have less diversity in its ecosystems resulting in fewer aquatic animals and plants compared to saltwater ecosystems. If you’re looking for variety, stick with saltwater diving. However, most of what you can see will be new to you if you’ve never dived in freshwater before.
Selecting the Perfect Freshwater Diving Location
Diving in freshwater requires the same level of dive planning as saltwater diving. A good location is key. A good rule of thumb is to avoid rivers because of their fast moving currents and shallow depths. Instead of a river, we recommend looking for nearby lakes and ponds.
To help you out with finding the perfect freshwater dive site, PADI has compiled a short list of freshwater dive sites that you can check out if they happen to be close to where you live. Keep in mind that the Playa Del Carmen in Mexico requires you to be PADI Cavern Diver certified to even attempt a dive there. In fact, many freshwater sites are home to expansive cave systems for the most adventurous of divers to improve their cave diving skills.
Regardless of which freshwater body you intend to dive in, you should do some thorough research into that area before committing on a trip. A quick Google search of the dive site’s name and “impressions” or “review” can most likely get you some valuable feedback from past divers.
Do some critical thinking and look for patterns in what’s being said about that dive site, both good and bad. If a diver complains that the site is bad because it’s too cold or something whiny like that, you can assume it’s because they did not come prepared with the right gear (discussed in the next section), and that it does not necessarily mean the site is actually bad.
In the winter, freshwater bodies of water such as lakes will often freeze over. If you have your ice diver certification, you and a few buddies can do some ice diving.
Freshwater vs. Saltwater Diving Gear
Thankfully, there are not many differences in necessary equipment for saltwater and freshwater diving. If you already own a set of gear for saltwater diving, you may be able to use the same set for freshwater diving. To reiterate, these pieces of gear are: a scuba mask, diving fins, a scuba tank and cold water regulator, dive weights, a buoyancy control device, and a dive computer.
So what differences in gear should be made for freshwater vs saltwater diving? Since freshwater is colder, if you plan on diving in it without getting hypothermia, you should consider getting a thicker wetsuit (>3mm or even a drysuit), dive booties, as well as thicker gloves and dive hood. Since freshwater is less buoyant, you need less dive weights. Additionally, you should adjust the setting in your dive computer so that it is calculating a dive profile for freshwater at a different altitude than sea level.
You can bring even more items, of course, however the gear mentioned above are the essentials. You may wish to bring a waterproof camera to capture the unique aquatic life that is exclusive to the freshwater ecosystem. You also can’t go wrong with bringing a dive torch and a trusty dive knife.
