Swimming Speed

Swimming Speed determines how fast the player moves in water. The swimming speeds on Subnautica and Subnautica: Below Zero are different, the latter being slightly slower.

The swim speed can be affected by: whether or not you swim underwater or on the surface, the suit(but not mask or gloves), oxygen tank, fins, holding tools and whether or not you have additional oxygen tanks in the inventory.

In Subnautica, the base swim speed is 5.75m/s underwater and 6.14m/s on the surface. With a Seaglide, the base value is 11m/s underwater and it doesn't work on the surface at all. The game then applies modifiers to these values:

Effects on Swimming Speed in Subnautica (in meters per second)
Modifier	Underwater (m/s)	Surface (m/s)
Fins	+1.41	+1.85
Ultra Glide Fins	+2.38	+3.12
Swim Charge Fins	0.00	0.00
Standard 02 Tank	-0.32	-0.42
High Capacity O2 Tank	-0.37	-0.50
Ultra High Capacity O2 Tank	-0.48	-0.62
Lightweight High Capacity Tank	-0.08	-0.10
Holding a Tool	-0.75	-0.97
Reinforced Dive Suit	-0.75	-0.97
Seaglide	Any other suit	Reinforced Dive Suit
Fins(any type)	0.00	0.00
Standard O2 Tank	-0.05	-0.32
High Capacity O2 Tank	-0.10	-0.37
Ultra High Capacity O2 Tank	-0.20	-0.48
Lightweight High Capacity Tank	0.00	-0.08
Suit	0.00	-0.48

Additional notes:

• The values may be off by 0.01-0.02 m/s because the values displayed are rounded to 0.01.
• Reinforced Dive Suit is the only suit with a speed penalty; Reinforced Gloves have no penalty and still provide 10% damage resistance.
• Ultra High Capacity Oxygen Tank has a speed penalty when you carry it in the inventory (-0.995m/s per tank in inventory); all other tanks have no such effect.
• Seaglide does not benefit from the fins at all but you can still use Swim Charge Fins to charge it as you go.
• Wearing the Reinforced Dive Suit has a very unusual effect on the speed of the Seaglide. Not only does it reduce it's speed itself, but also return the speed penalties for equipping oxygen tanks to their base values when swimming without a Seaglide.

In Below Zero, these values are different. The base swim speed is 4.54m/s underwater, and 4.88m/s on the surface. The game then applies modifiers to these values:

Effects on Swimming Speed in Below Zero (in meters per second)
Modifier	Underwater (m/s)	Surface (m/s)
Fins	+1.50	+1.09
Swim Charge Fins	0.00	0.00
Seaglide	+2.62	n/a
Standard 02 Tank	-0.32	-0.42
High Capacity O2 Tank	-0.37	-0.50
Ultra High Capacity O2 Tank	-0.48	-0.62
Ultra High Capacity O2 Tank (in inventory)	-0.95	-1.25
Booster Tank	-0.37	-0.50
Booster Tank boost	+3.00	+2.61
Booster Tank boost with Seaglide	+4.12	n/a
Holding a Tool	-0.75	-0.98
Reinforced Dive Suit	-0.75	-0.98
Exploring the Mercury II	-1.53	n/a

Additional notes:

• The values may be off by 0.01-0.02 because the values displayed are rounded to 0.01.
• Reinforced Dive Suit and Ultra High Capacity O2 Tank function the same in both games
• Unlike the previous game, Below Zero's Seaglide speed is affected by other speed buffs and debuffs. Fins make it faster, and tanks slow it down.
• The Booster Tank boost can be used in the surface, but once it reaches maximum speed, momentum is lost.