Wed Jan 1

The surprising ways ‘swimming off’ a hangover can be risky, even if alcohol has left your system

Written by: Amy Peden, NHMRC Research Fellow, School of Population Health & co-founder UNSW Beach Safety Research Group, UNSW Sydney

It’s the morning after a big night and you’re feeling the effects of too much alcohol.

So it can be tempting to “refresh” and take the edge off a hangover with a swim at the beach, or a dip in the cool waters of your local river or pool.

But you might want to think twice.

The day after heavy drinking can affect your body, energy levels and perception of risk in many ways. This means you’re more likely to drown or make careless decisions – even without high levels of alcohol in your blood.

Alcohol + water + summer = drowning

Alcohol is one of the main reasons why someone’s more likely ^[1] to die due to drowning. And Australians consume a lot of it ^[2], including around the water ^[3].

The risk of drowning, and injury, including incidents involving alcohol, dramatically increases over the summer festive period ^[4] – in particular on public holidays ^[5] and long weekends ^[6].

Among people aged 18 and over who drowned in rivers where alcohol was involved, we found some 40%^[7] had a blood alcohol concentration of at least 0.20%. That’s four times the upper legal limit of 0.05%^[8] when driving a car on a full licence.

When we breathalysed ^[9] people at four Australian rivers, we found higher levels of blood alcohol with higher temperatures, and particularly on public holidays.

At the beach, intoxication due to alcohol and/or drugs is involved in 23% of drowning deaths ^[10] with an average blood alcohol concentration of 0.19%.

How about if you’re hungover?

Getting alcohol out of your body is a relatively slow process. On average, alcohol is metabolised at a rate of 0.015% per hour ^[11]. So if someone stops drinking at 2am with a blood alcohol concentration of 0.20%, their alcohol levels don’t drop to zero until 4pm the next day ^[12].

Although hangovers can vary from person to person, typical symptoms ^[13] include headache, muscle aches, fatigue, weakness, thirst, nausea, stomach pain, vertigo, irritability, sensitivity to light and sound, anxiety, sweating and increased blood pressure.

As well as feeling a bit dusty, the day after an evening of heavy drinking, you’re not so good at identifying risks and reacting to them ^[14].

In a pool, this might mean not noticing it’s too shallow to dive safely. In natural waterways, this might mean not noticing a strong river current or a rip current at the beach. Or someone might notice these hazards but swim or dive in anyway.

Young adults in inflatable boats, lilos on river, relaxing

You don’t have to have alcohol in your blood to be affected. Fatigue can set in, leading you to make careless decisions. tismaja/Shutterstock ^[15]

In one study ^[16], we found that after a four-day Australian music festival where people drank heavily, even people who were sober (no longer had alcohol in their blood) were still affected.

Compared to baseline tests in the lab we ran three weeks before the festival, people who were sober the day after the festival had faster reaction times in a test to gauge their attention. But they made more mistakes. This suggests hangovers coupled with fatigue lead to quicker but more careless behaviour.

In and around water this could be the difference between life and death.

Positive blood alcohol readings, including of alcohol from the night before, are commonly implicated in drowning deaths as a result of risky behaviours such as jumping into the water, both at a river ^[17] and along the coast ^[18]. Jumping can cause physical injury or render you unconscious, leading to drowning.

Alcohol, including the day after drinking, can also make drowning more likely for a number of other reasons ^[19]. It also reduces people’s coordination and reaction times.

What else is going on?

Alcohol makes the blood vessels near your skin open up (dilate). So more blood flows into them, making you feel hot. This means you may stay in colder water for longer, increasing your risk of hypothermia.

Alcohol can even make CPR (cardiopulmonary resuscitation) less effective ^[20], should you need to be resuscitated.

Normally, your body controls levels of certain minerals (or electrolytes) in the blood. But electrolyte imbalance is common ^[21] after heavy drinking, including the day after. It’s the reason why hangover symptoms such as muscle pain can lead to cramps in your arms or legs. This can become dangerous when being in or on the water.

Low blood sugar levels the day after drinking is also common ^[22]. This can lead to people becoming exhausted more quickly when doing physical activities, including swimming.

Other hazards include cold water, high waves and deep water, all of which your body may not be capable of dealing with if you’re feeling the effects of a big night.

What can we do about it?

Authorities regularly warn about the dangers ^[23] of alcohol intoxication and being near the water. Young people and men are often targeted because these are the groups more likely to drown where alcohol is involved ^[24].

Beaches may have alcohol-free zones. Rivers rarely have the same rules, despite similar dangers.

Royal Life Saving urges men to ‘make the right call’ and avoid alcohol around the water.

How to stay safe around water if you’re drinking

So take care this summer and stay out of the water if you’re not feeling your best:

do your swimming before your drinking
look out for your mates, especially ones who may have had a few too many or are hungover
avoid getting back into the water after you’ve drunk alcohol or if you’re not feeling your best the next day.