Question: What is it called when a person uses a diving mask, snorkel and fins, to swim through a body of water?
About the article "Snorkeling", section "Abstract".

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Action figure and Snorkel set.
A scuba diving action figure featuring removable mask, fins, wet-suit, scuba tank, and horse collar Buoyancy compensator (diving) was produced for the film.
In addition a Snorkel set consisting of a mask, snorkel and fins were made. 
[[File:AnnotatedOctopushPlayer.png|left|thumb|200px|Annotated Player 1. snorkel and mouthguard 2. hat with earguards 3. mask 4. fins 5. stick 6. puck 7. glovePlayers wear a diving mask, snorkel and fins, and carry in one hand a short stick for playing the puck.
A full list of equipment is given below: 
Snorkeling (British and Commonwealth English spelling: snorkelling) is the practice of swimming on or through a body of water while equipped with a diving mask, a shaped tube called a snorkel, and usually fins.
In cooler waters, a wetsuit may also be worn.
Use of this equipment allows the snorkeler to observe underwater attractions for extended periods of time with relatively little effort.
Snorkeling is a popular recreational activity, particularly at tropical resort and scuba diving locations.
The primary appeal is the opportunity to observe underwater life in a natural setting without the complicated equipment and training required for scuba diving.
It appeals to all ages because of how little effort there is, and without the exhaled bubbles of scuba-diving equipment.
It is the basis of the two surface disciplines of the underwater sport of finswimming.
Snorkeling is also used by scuba divers when on the surface, in underwater sports such as underwater hockey and underwater rugby, and as part of water-based searches conducted by search and rescue teams.
Methods of underwater diving.
Diving without breathing apparatus.
Underwater diving without breathing apparatus can be loosely categorized as underwater swimming, snorkeling and free diving.
These categories overlap considerably.
Several competitive underwater sports are practiced without breathing apparatus.
The ability to dive and swim underwater while holding one's breath can be a useful emergency skill, and is an important part of water sport and navy safety training.
More generally, entering water from a height is an enjoyable leisure activity, as is underwater swimming without breathing apparatus.
Free diving does not involve the use of external breathing devices, but relies on a diver's ability to hold his or her breath until resurfacing.
It includes a range of activities from simple breath-hold diving to competitive apnea dives.
Fins and a diving mask are often used in free diving to improve vision and provide more efficient propulsion.
The use of a short breathing tube known as a snorkel allows the diver to breathe with the face remaining immersed, while at the surface.
This may also be used when no diving is intended, and the snorkeler remains at he surface. 
The SCUBA equipment listed under the T/E set by the US Navy for the Marine Corps reconnaissance: Draeger LAR V rebreather unit — The rebreather unit is a SCUBA system that scrubs exhaled carbon dioxide and recycles it into breathable nitrogen/oxygen mixed gas.
Since it is closed-circuit, a trail of air bubbles does not reach the water's surface, which would reveal the location of the diver and compromise the mission.
Deep See Squeeze Lock – diving knife with a beta-titanium blade.
Useful when snagged in fishing nests or other submerged entanglements alike, when swimming underwater are almost non-visible.
Aqua Lung Military Snorkel Flex Tube — Standard-issue snorkel.
Aqua Lung Rocket Fin — Standard-issue swimfins.
Aqua Lung Look Mask and Mythos Mask — Standard-issue diving mask.
Mythos mask contains a blow-out, one-way valve at the nasal piece to expel water that is in the goggles.
Diver's Weight Belt, (WB67/WB68) – Weight belt is used to level buoyancy under the water.
Case Soft Diving Weights, (September-M-2/Sep-M-5) – Additional weights that can be released individually to proper buoyant level.
Scubapro Twin Jet Fins — Split fins are fairly new to the Marine Corps T/E, since 2000.
They have been tested to prove that the split fin design allows slightly better maneuverability if one had to immediately run during unexpected enemy contact once ashore.
It also has excellent water propulsion to push the recon Marines and Corpsmen to shore.
Aqua Lung Impulse 2 Snorkel — This snorkel contains a one-way valve that prevents water from entering the diver's mouth.
UDT life preserver — Standard-issued life preserver.