Any one who wishes to become a British Royal Marine has first to take an intelligence test at the recruiting office.
If they pass it they cant become a Marine.
The rest of the armed forces always found it ironic that troops with a decidedly water dedicated role were so averse at having the stuff actually touch their skins(and dont even mention soap)
Its a bit like the crabfats being afraid of heights or the rest of the navy not being interested in dressing up in womens clothing and hating hairdressing.
Thank god we’ve got an army.