Health checks before you start

Most healthy adults and children can learn mermaiding or underwater dance. Some health conditions, though, make breath-holding, swimming in a tail or changes in pressure riskier. The answer is rarely "never". More often it is "check first, and plan around it".

This guide lists the conditions worth raising with your doctor, and explains in plain words why each matters in the water. It cannot tell you whether you personally are fit to swim. Only your doctor can do that.

Why the water is different

A few things happen in mermaiding and underwater dance that do not happen on land:

• You hold your breath. Your body runs on the oxygen you took down with you.
• Your face is in the water. Scientific American describes the dive reflex, set off by putting your face in cold water: the heart slows a little and blood vessels in the arms and legs narrow.
• Pressure changes. Even a few metres down, pressure acts on your ears, sinuses and lungs. See Equalising your ears.
• Your legs are joined, if you wear a tail, so getting upright or to the edge takes longer.
• Any moment of confusion or faintness is more dangerous when your head is under water.

That last point is the thread running through most of the list below.

Conditions to check with your doctor first

Heart and blood pressure

Heart conditions, high or low blood pressure, heart rhythm problems, or a history of fainting or chest pain with exercise.

Why: breath-holding and the dive reflex change your heart rate and circulation. Anything that could make you faint, or strain your heart, is far more serious underwater than on land.

Epilepsy and seizures

Including any condition, or past episode, that has caused a sudden loss of consciousness.

Why: a seizure in the water can stop you keeping your face clear. The Epilepsy Society advises swimming with someone who knows how to help in a seizure, and telling pool lifeguards how to help you. It also says scuba diving is not recommended for people who have seizures, because a seizure underwater can endanger both the diver and their buddy. Breath-hold work deserves the same careful conversation with your doctor or epilepsy nurse.

Asthma

Especially asthma triggered by exercise, cold or chlorine.

Why: breath-holding and exertion put demands on your lungs, and an attack in the water is hard to manage. Swim England advises keeping your reliever inhaler close at all times, warming up properly, and not swimming on days when your symptoms are troubling or you have a bad cold. If swimming seems to make your asthma worse, see your doctor.

Other lung conditions

Such as a past collapsed lung, recent chest surgery, or any ongoing lung disease.

Why: breath-holding and pressure changes put strain on the lungs. Your doctor can tell you whether your lungs are ready for it.

Diabetes

Particularly if you use insulin or other medicines that can cause low blood sugar.

Why: a hypo in the water can cause confusion or faintness at the worst moment. Diabetes UK notes that swimming can lower blood sugar, with an effect that can last up to 48 hours, and that insulin doses may need adjusting on swimming days, which your diabetes team can advise on. It advises checking your levels more often and letting someone at the pool know you have diabetes. We would add: keep your hypo treatment within reach at the poolside, not in a locker. Diabetes UK also warns that, in open water, the usual warning signs of a hypo can be harder to notice.

Ears, nose and sinuses

Recent ear infections, ear surgery, a perforated eardrum, ongoing sinus problems, or trouble with ears on planes.

Why: you need to equalise your ears as you go down. Divers Alert Network (DAN) explains that colds, allergies, sinus trouble, smoking and a crooked septum can all make that harder. A damaged or healing ear needs your doctor's go-ahead before it goes under water.

Recent surgery, injury or back problems

Especially to the back, hips, knees or ankles, which the dolphin kick works hard.

Why: a tail joins your legs and puts the effort through your core and lower back. Healing tissue needs time.

Pregnancy

Why: your doctor or midwife knows your pregnancy, and we would always want their advice before breath-holding or swimming in a tail. Please tell us if you are, or might be, pregnant.

Anxiety or panic in water

This is not a medical bar, and it is more common than people think.

Why: panic makes you breathe fast and fight the water, which is exactly what a breath-hold needs you not to do. Tell us, and we will go at a pace that suits you.

Medication

Any medicine that makes you drowsy, or affects your heart, breathing, balance or blood sugar.

Why: the US Centers for Disease Control and Prevention (CDC) notes that some medicines, including some for anxiety and mental health, can affect balance and judgement in the water. Do not stop or change a medicine on your own; ask your doctor how it fits with swimming.

Children

Everything above applies to children too. Children may not mention symptoms, so it is up to parents to tell us. Anyone under 18 needs a parent's consent for our courses, and an adult must be at the pool for children under 16. See our guide for parents.

Do not swim that day if

• You have a cold, a blocked nose, or an ear or sinus infection. MedlinePlus, the US National Library of Medicine's health site, warns that diving while congested can make an ear injury worse.
• You feel unwell, feverish or dizzy.
• You are very tired, or have slept badly.
• You have had alcohol. The CDC notes that alcohol affects judgement, balance and coordination.
• You have had a heavy meal just before.
• You blacked out or lost control in the water recently. A DAN article by Capps advises staying out of the water for at least 24 hours, and StatPearls advises a hospital check after any loss of consciousness in the water.

Missing a lesson is disappointing. Swimming through one of these is not worth it. Let us know, and we will find another time.

Your health declaration

MFI requires a health declaration before any course begins, and we ask about your health on every path. It asks about your health, and it exists for one reason: so your instructor can keep you safe.

Please be honest on it. Leaving something out does not make you safer; it only means your instructor cannot plan for it. A condition you declare is something we can work around. One we do not know about is a risk we cannot see.

If you answer yes to something, it does not automatically mean you cannot take part. It usually means a conversation, and sometimes a note from your doctor first.

Tell your instructor

On the form and in person, tell us everything relevant, even if it seems small:

• Any condition, past or present
• Any medication, including inhalers and insulin, and where you keep it at the pool
• Past injuries or surgery
• Anything your doctor has told you about exercise or swimming
• How you feel on the day

Your health information is kept private and used only to teach you safely. Our Privacy Policy explains how we keep it.

Common mistakes

• "It's only a pool." Breath-holding and pressure work the same way in a pool as anywhere else.
• "It was years ago." Old conditions, such as a past collapsed lung or seizures, still matter. Mention them.
• "I didn't want to be turned away." Most conditions mean adjusting, not refusing.
• Leaving medication in the locker. An inhaler or hypo treatment is only useful within reach.
• Swimming with a cold to avoid missing a session.

In our lessons

Lessons are mostly one-to-one, and Aliyah adjusts the pace, depth and length of breath-holds to suit you. She will ask how you are feeling before you get in, and you can stop at any point.

This guide cannot cover every condition. If you are unsure about anything, ask your doctor before you book, and ask us if you have questions about what a lesson involves.