Many believe that it is unsafe to swim immediately after having a meal and that it is preferable to wait at least 30 minutes. The fear is that swimming can cause stomach cramps and muscle cramps with discomfort and potentially drowning.

With this randomized controlled trial, the aim was to investigate whether there was any hold in this belief and what could potentially happen by swimming with the stomach full immediately after a meal.

All volunteers will be adults. Participants will receive both oral and written information about the trial prior to giving consent for participation.

Participants will act as their own control over two days. On the first day, participants will be randomized to either swim immediately after they have eaten their usual lunch or 30 minutes after the last bite. They will do the opposite on the second day. The randomization will be done by throwing a dice.

Prior to swimming, participants will fill out the following:

• Visual analogue scale (VAS) about their well-being
• Questionnaire about their mood state

After swimming, participants will fill out the following:

• Visual analogue scale (VAS) about their well-being
• Questionnaire about their mood state
• Adverse events

Prior to swimming and afterwards, the participants' blood pressure, pulse, and blood oxygen levels will be measured.

Sample size: Convenience sample.

Withdrawal and dropout criteria: All participants will be informed that they can withdraw their consent at any point during the trial without having to explain any reasons.

Inclusion Criteria:

• ≥18 years
• Healthy volunteers
• Otherwise, no restriction since each participant acts as their own control

Exclusion Criteria:

• Smoking one hour prior to swimming
• Participants who cannot swim