Drowning is a lack of oxygen, and its resuscitation is the one common adjustment to standard basic life support.
Five rescue breaths first, before compressions. Standard adult resuscitation begins with compressions; drowning does not, because the problem is oxygen rather than circulation. The European Resuscitation Council guidance states this explicitly.
Then thirty compressions to two breaths, as usual: centre of the chest, 5–6 cm, 100–120 a minute.
Do not attempt to drain water from the lungs. Pressing on the abdomen or tipping the casualty delays resuscitation and causes vomiting and aspiration. The guidance is unambiguous.
Expect vomiting. It is common in drowning resuscitation. Turn the head, clear the mouth, continue.
Keep them warm. Wet clothing off where you can, cover them, shelter them from wind. Hypothermia and drowning arrive together.
Everybody who was submerged goes to hospital, including people who recover completely and feel fine. Deterioration hours later is a recognised pattern.
Source. European Resuscitation Council Guidelines 2021 — Drowning, https://cprguidelines.eu/ ; ILCOR, https://www.ilcor.org/
This is reading, not training. An accredited course is what puts this in your hands rather than in your memory.