This is a monocentric pilot study to assess the safety profile of a 30-meter deep underwater diving using 3 different type of gas mixtures: AIR (21% O2 and 79% N2), NITROX 32 (32% O2 And 68% N2) and TRIMIX (21% O2, 44% N2 and 35% He).

The participants will be measured for vital parameters, blood samples and transthoracic cardiac ultrasound before diving (baseline).

Participants will be requested to perform recreational dive, which does not require particular decompression stops, at a depth of 30 meters with a 30 minutes botton time. 20 minutes after dive the same measurements as baseline will be repeated, once at rest and once after a physical effort by performing a series of 10 bending on the legs (squats). The day after dive, the participants will be interviewed by phone (FOLLOW-UP) by a physician. It will be required to report any unusual event, MDD symptom, or neurological complication.

Same procedure will be repeated with three different type of blends (AIR, NITROX, TRIMIX).

Inclusion Criteria:

• Age 18 - 60
• healthy subjects
• body mass BMI < a 30
• physical status ASA 1

Exclusion Criteria:

• subjects with significant clinical impairments such as important head trauma, general pain, low back pain, diabetes, asthma, cardiac and coagulation dysfunctions
• pregnant women
• participation in another study in the last 3 months
• use of drugs and alcohol
• smoking
• psychiatric disorder

Healty volunteer divers