Very bad idea!!! WD40
In scuba your body absorbs things more rapidly and at higher concentrations lubricants used should be food grade.
Check with a professional on what can be safely used and where and how to use it
If you should not eat it or breath it don’t use it!!!
Look at the material safety data sheet for WD40 some of the following statements.
Quotes under #2 danger, flamable, harmfull or fatal if swallowed. if swallowed may be aspirated and cause lung damage,inhalation high concentrations may causenasal and respitory irritation and nervous effects such as headache,dizziness and nausea, swallowingmay cause gastrointestinal irritation ,nasea, diarhea. if swallowed can enter the lungs and cause chemical pneumonitis, severe lung damage and death.
Be safe and have fun diving