Water polo cap colors and cap numbers explained
The cap is doing two jobs at once. It tells you which team a player is on (white, dark, or red), and the number on the side tells you who that player is. Here is the full breakdown — the three colors, the red-cap goalkeeper rule, and the cap-1 convention.
By Eggbeater Water Polo · May 27, 2026 · 6 min read
A water polo cap is a tiny piece of equipment that does an outsized amount of work. It keeps the ears safe from incoming shots, it tells the referees who is on which team during a 20-second swim, and it lets spectators follow a single player through a chaotic six-on-six. The system has been the same for decades, and once you understand the three colors and the cap-1 convention, the sport gets dramatically easier to watch.
1. The three cap colors at senior level
The three-color system
Two teams of seven players each, three colors total. If you see two reds on the deck at warm-up, you are looking at the starting goalkeeper from each team.
At the senior FINA / World Aquatics level, the cap colors are fixed: white, dark (typically blue), and red. Some lower-level leagues and youth tournaments use black, navy, green, or another dark color instead of blue — the only requirement is that the dark cap is clearly distinguishable from the white cap and from the red cap from the deck and from the underwater cameras. A team in dark green caps is playing under a perfectly legal variant.
The team that wears white versus dark is decided by the schedule or the tournament packet, not by who is hosting. In knockout-round play, the higher seed often wears white, but local tournaments vary. The away team typically packs both sets of caps to the pool so they can switch if the bracket says so.
2. Why caps and not jerseys
Two reasons, and both come straight from the pool.
Reason one: visibility. A water polo player is underwater for roughly ninety percent of the game. Treading water with the eggbeater kick keeps the head and shoulders up, but the torso is submerged. A jersey would be visible for only a few seconds per possession. The cap stays above water on every stroke, every defensive press, every shot, every swim back to half. Whatever color and number is on the cap, the referees and the scorer can see it the entire time.
Reason two: ear protection. A water polo ball travels fast. Elite shots hit the cage at speeds above 70 km/h, and even routine passes are firm enough to bruise an unprotected ear. The cap has rigid plastic ear guards stitched in on both sides. They protect the cartilage from balls, from elbows, and from the occasional swimming-pool collision. Coaches insist on caps from the first day of Splash Ball precisely because of this — a torn cartilage from one freak shot can mean weeks out of the water.
The cap also has a chin strap. It buckles or velcros under the chin so the cap stays on during shots, presses, and underwater wrestling. A cap that falls off is a problem during play, and we will get to that in section 6.
3. The red cap rule for goalkeepers
Goalkeepers always wear red. This is one of the few rules in water polo with almost no exceptions.
The reason is visual unambiguity. Goalkeepers have privileges that no other player has — they can use both hands at the same time, they can stand on the bottom inside the 5-meter line, they cannot legally cross the half-distance line during open play. When a referee blows the whistle, those distinctions need to be settled in a fraction of a second from anywhere on the deck. The red cap makes the goalkeeper visually unique. Even a referee glancing at the cage from twenty meters away knows instantly who the goalkeeper is.
That logic is why the rule survives even when team colors clash. If a team’s primary color is red, the goalkeeper still wears a red cap. The field players might wear white or dark, the team kit might be red, but on the deck and in the water the red cap is reserved for the GK. This is uniform across FINA, NCAA, USA Water Polo, NFHS, and almost every domestic league.
For new spectators — how to spot the goalkeeper instantly: walk in during warm-up, find the only red cap on the deck for each team. That is your starting GK. During the game, look at the cage — the player closest to the back wall wearing red is who you are watching. If a second red cap appears in the middle of the game, that is the backup GK coming in for a substitution.
4. The numbering convention (1 to 13)
Cap numbers in water polo run from 1 through 13 at the senior FINA level, though some leagues use 1 through 11 or even 1 through 15 depending on roster sizes.
The numbers are printed in large block characters on both sides of the cap. White-cap numbers are usually printed in blue or black. Dark-cap numbers are usually printed in white or yellow. Red-cap numbers are usually printed in white. The goal is contrast — the number has to read clearly from the scorer’s bench, from the underwater cameras, and from the spectator stands.
| Cap number | Who typically wears it | Convention strength |
|---|---|---|
| 1 | Starting goalkeeper | Near-universal — FINA / NCAA / USA Water Polo / NFHS |
| 2 – 12 | Field players, any role | Roster-defined — varies by team |
| 13 | Backup goalkeeper (where used) | Strong convention at senior level; optional at youth level |
| 14 – 15 | Reserve field players (where rosters are extended) | League-dependent |
Cap numbers must be unique within a single team for a single game. Two players on the same team cannot both wear cap 7 in the same match. But across the two opposing teams, duplicates are fine — the cap color disambiguates. A scoresheet will record a goal by White 7 versus Blue 7 as two completely separate stat lines.
Some leagues require that cap numbers match the player’s roster number on the scoresheet. If your roster lists Sarah as #7, she wears cap 7. Other leagues allow the cap number to differ from the roster number, as long as the roster sheet maps the two. Check your tournament packet or league rulebook to be sure.
5. Cap 1: the starting goalkeeper
Of all the cap-number conventions in water polo, the one that holds up everywhere is cap 1 = starting goalkeeper. From a 10U Splash Ball game in California to the Olympic final, the player wearing the red cap with a “1” on the side is the GK who starts the game in the cage.
This convention is so well-established that broadcasters, scorers, and live-scoring apps assume it. The Eggbeater scorer, for example, defaults the cap-1 slot to “GK” and labels stats accordingly — saves and goals-against tally to the cap-1 player by default, and the volunteer at the desk only needs to override when the backup goalkeeper comes in.
The backup goalkeeper, where rostered, traditionally wears cap 13. The number 13 is set aside as the “second red cap.” When a substitution happens at the goalkeeper position, the cap-1 player swims to the bench, the cap-13 player swims to the cage, and play resumes. Both wear red — that is non-negotiable — but the numbers tell the scorer which goalkeeper to credit on the next save.
For coaches — distributing caps before the game: hand caps out three minutes before the opening whistle, not three seconds. Field players need time to strap the chin band, tighten the ear guards, and double-check the number. Pack at least two spare caps per game in the team bag — one for an emergency strap break, one for a player who switches positions mid-game. Spare caps should include a spare red so a backup GK can step in without a scramble.
6. Cap durability rules during play
A water polo cap is supposed to stay on, strapped under the chin, throughout play. The strap is the load-bearing part of the system. Without it, every defensive press or shot would knock the cap off.
What happens if a cap comes off depends on how it came off:
- Defensive foul caused it. If a defender grabs another player’s cap and pulls it off — particularly during a swim or a shot attempt — that is typically called as an ordinary foul, or an exclusion (kickout) if the action interfered with an obvious goal-scoring opportunity. The cap-pull is one of the classic “tactical fouls” the referees watch for.
- It just slipped off. If the strap loosens on its own and the cap comes off in open play, the referee waits for the next dead ball, then halts play long enough for the player to re-strap or get a spare cap from the bench. Play does not stop mid-possession unless the cap creates a safety risk.
- It’s stuck to the lane line. Rarely, a cap that comes off mid-game ends up tangled in a lane rope. Same rule — deal with it at the next dead ball, swap in a spare cap, resume play.
Coaches teach swimmers to cinch the strap tight at the start of each quarter. Loose straps come off — not in a “the cap fell off” way, but in a “the defender yanked it off intentionally” way — and a cap-pull called as a kickout puts the team a player down for twenty seconds. It is a small detail that decides games.
7. How spectators track a player
Here is the trick that makes water polo dramatically easier to watch for the first time: memorize the cap number of one or two players you care about. The cap number is the only durable visual identifier during the swim. Hair color, swim style, body type — all of these disappear underwater. The cap stays up.
Examples that work for first-time spectators:
- “My kid is cap 7.” One number. Watch for cap 7 in your team’s color. You will find them within a possession or two.
- “The hole set is cap 4.” Hole set (the center forward) is the player who plants in front of the cage two meters out. Once you know their cap number, every offensive possession suddenly makes sense.
- “The driver is cap 9.” Drivers swim a lot and create from the perimeter. Memorize one driver’s cap and you can follow how the offense flows.
If you are watching multiple games in a tournament weekend, you will start to recognize cap numbers without trying. Coaches do the same thing — an opposing coach scouting a game does not need to know the names on the roster, only the cap numbers of the key threats. “Their cap 6 is the lefty shooter, double-team on the post-up” is enough information for a half-time talk.
For a deeper look at what each cap-number-and-role combination is doing in the water, see our positions guide — it pairs cap numbers with the seven roles (goalkeeper, hole set, point, two wings, two drivers, and the hole defender). Cap colors plus positions together are the visual shorthand that turns a confusing six-on-six into a watchable game.
Cap colors are the first lesson. What’s next?
If you found this useful, two more spectator basics will get you to “yes, I actually understand what’s happening” within a single game: the positions every player swims, and the scoring rules that decide which whistles matter.
Positions explained →Frequently asked questions
Goalkeepers wear red caps so that referees, scorers, and the other six players can instantly identify them from anywhere in the pool. Goalkeepers have rules that no other player has (they can use two hands, they can stand on the bottom inside 5 meters, they cannot cross half), so the red cap makes those special privileges visually unambiguous. The rule applies to both teams: even if a team’s color is red, the goalkeeper still wears a red cap.
There are three cap colors in a standard water polo game. White caps are worn by the field players on one team. Dark caps (usually blue, but sometimes black or another distinguishable dark color) are worn by the field players on the other team. Red caps are worn by the goalkeepers of both teams. The home team designation does not always pick the colors; the schedule, the rule set, or the tournament packet decides which team wears which color.
By convention, the starting goalkeeper wears cap number 1, and the backup goalkeeper wears cap number 13 (where used). The number is on the side of the red cap, just like every other player. Some leagues let goalkeepers wear other numbers if their roster sheet says so, but cap 1 = starting GK is a near-universal convention from youth water polo through the senior FINA / World Aquatics level.
Yes. Cap numbers only need to be unique within a single team for a single game. Two players can wear cap 7 on opposite teams in the same game with no problem — the white-versus-dark cap color already disambiguates them. Scoresheets list players as “White 7” or “Blue 7” (or “Dark 7”) to keep stats straight.
Players spend roughly ninety percent of a water polo game underwater. A torso jersey would be invisible from the deck most of the time, and any printed number would distort as the fabric clung to a player’s body. The cap stays above water on every stroke, every defensive press, and every shot. Caps also protect the ears from incoming shots — water polo balls travel fast and ear injuries are common without the cap’s built-in ear guards.
Caps must remain strapped under the chin throughout play. If a cap comes off during a defensive action — for example, a defender pulls another player’s cap off — that is typically called as an ordinary foul (or an exclusion if it interferes with an obvious goal-scoring opportunity). If the cap simply slips off in a swim or a shot, the referee will halt play at the next dead ball so the player can re-strap or get a spare cap from the bench.