What's the insect that bites you in the sand? And what can be the consequences

Where? On a beach of the West African coast at night. Been on that same beach during the day and everything was fine

Type of insect? Pretty aggressive, everyone had at least 20 bites after few minutes

Type of bites? Look like mosquito bites, but the bumps are way more red, swollen and itchy even after 2 days. Bites concentrated on the areas that were in contact with sand, instead of the usual zones like ankles.

A quick Google search points towards sand flies, but the bites don't correspond. Any idea?

Thanks a lot