What is the equipment in Open Water Swimming?

Verdict

Swimwear: at a water temperature of 18.0°C or above, an Athlete must wear one swimsuit in one or two pieces (not a wetsuit) that has been approved under Article 6 of Part One (Article 10.1 of Part Three).; Wetsuit: at a water temperature below 18.0°C, an Athlete must wear a wetsuit, with only one...

Source: Article 6, Article 10.1, Article 10.2, Article 10.3, Article 10.7, Article 7.8, Article 12.3.1, Article 10.8, Article 10, Article 4.4, Article 4.4.2 — World Aquatics Competition Regulations – Part Three: Open Water Swimming Rules

Section 2: Equipment

Swimwear: at a water temperature of 18.0°C or above, an Athlete must wear one swimsuit in one or two pieces (not a wetsuit) that has been approved under Article 6 of Part One (Article 10.1 of Part Three).
Wetsuit: at a water temperature below 18.0°C, an Athlete must wear a wetsuit, with only one swimsuit permitted underneath (Article 10.2 of Part Three). If the water temperature is between 18.0°C and 20.0°C and the Chief Referee, on the advice of the Safety Officer and Medical Officer, determines conditions are hazardous, the Chief Referee may require all Athletes to compete in wetsuits (Article 10.3 of Part Three).
Cap: every Athlete must start the race wearing one or two approved caps in accordance with Articles 6.10 and 7.8.6 of Part One (Article 10.1–10.2 of Part Three); a swimmer wearing an unapproved cap, or two caps where either is unapproved, is disqualified (Appendix 7, items 6–7, of Part Three). Athletes competing as a team must wear a team cap of identical colour and style (Article 10.7 of Part Three, Article 7.8 of Part One).
Microchip transponders: each Athlete must start the race wearing two microchip transponders, one on each wrist; if a transponder is lost or becomes detached during the race, race officials will issue a replacement, and an Athlete who finishes without at least one transponder is disqualified (Articles 4.1.8–4.1.9 of Part Three). The transponders provide split and finish times to an accuracy of one tenth of a second when used with Automatic Officiating Equipment (Article 12.3.1 of Part Three).
Goggles, nose clip, ear plugs: permitted where approved under Article 6 of Part One (Article 10.1 of Part Three), but not mandatory.
Technology and wearables: devices such as drones, GPS trackers, or bio-medical sensors are not permitted unless approved in advance and listed on the World Aquatics current list of approved wearables; any technology or wearable used must be declared in the first call room, and failure to declare results in disqualification (Article 10.8 of Part Three).
No fins, paddles, webbed gloves, or other devices that aid speed, buoyancy, or endurance are permitted beyond what Article 10 of Part Three allows; Athletes must also have trimmed fingernails and toenails and must not wear jewellery, including watches (Articles 10.4–10.6, 2.19.1 of Part Three).
Feeding equipment: nutrition passed to an Athlete during the race must be in a biodegradable container, handed by hand or by a feeding pole no longer than five metres bearing no more than one national flag of maximum 30 cm x 20 cm (Article 4.4 of Part Three); Athletes may not carry gels or other packaged nutrition in their swimwear (Article 4.4.2 of Part Three).

Section 2: Equipment

Swimwear: at a water temperature of 18.0°C or above, an Athlete must wear one swimsuit in one or two pieces (not a wetsuit) that has been approved under Article 6 of Part One (Article 10.1 of Part Three).

Wetsuit: at a water temperature below 18.0°C, an Athlete must wear a wetsuit, with only one swimsuit permitted underneath (Article 10.2 of Part Three). If the water temperature is between 18.0°C and 20.0°C and the Chief Referee, on the advice of the Safety Officer and Medical Officer, determines conditions are hazardous, the Chief Referee may require all Athletes to compete in wetsuits (Article 10.3 of Part Three).

Cap: every Athlete must start the race wearing one or two approved caps in accordance with Articles 6.10 and 7.8.6 of Part One (Article 10.1–10.2 of Part Three); a swimmer wearing an unapproved cap, or two caps where either is unapproved, is disqualified (Appendix 7, items 6–7, of Part Three). Athletes competing as a team must wear a team cap of identical colour and style (Article 10.7 of Part Three, Article 7.8 of Part One).

Microchip transponders: each Athlete must start the race wearing two microchip transponders, one on each wrist; if a transponder is lost or becomes detached during the race, race officials will issue a replacement, and an Athlete who finishes without at least one transponder is disqualified (Articles 4.1.8–4.1.9 of Part Three). The transponders provide split and finish times to an accuracy of one tenth of a second when used with Automatic Officiating Equipment (Article 12.3.1 of Part Three).

Goggles, nose clip, ear plugs: permitted where approved under Article 6 of Part One (Article 10.1 of Part Three), but not mandatory.

Technology and wearables: devices such as drones, GPS trackers, or bio-medical sensors are not permitted unless approved in advance and listed on the World Aquatics current list of approved wearables; any technology or wearable used must be declared in the first call room, and failure to declare results in disqualification (Article 10.8 of Part Three).

No fins, paddles, webbed gloves, or other devices that aid speed, buoyancy, or endurance are permitted beyond what Article 10 of Part Three allows; Athletes must also have trimmed fingernails and toenails and must not wear jewellery, including watches (Articles 10.4–10.6, 2.19.1 of Part Three).

Feeding equipment: nutrition passed to an Athlete during the race must be in a biodegradable container, handed by hand or by a feeding pole no longer than five metres bearing no more than one national flag of maximum 30 cm x 20 cm (Article 4.4 of Part Three); Athletes may not carry gels or other packaged nutrition in their swimwear (Article 4.4.2 of Part Three).

Section 2: Equipment