Number one danger on the beach is stupid 4x4/quad bike drivers! quickly followed by the amount of garabe that visitors to the beach kindly leave behind in black bags for the foxes to redistribute.

There are numerous species of shark in qatari waters, no records of attacks that i know of and likely never will be.

Sea snakes wouldn't bite you unless you harass them - then you probably deserve it!

Stonefish, stingrays etc. are prety rare for beach paddlers and general move away before you get ontop of them.

Jellyfish - these are a potneital problem especially for those with sensitive skin. Wear a lycra jumpsuit, you can get them that have good SPF aswell thus protecting from sunburn.

The best beaches are in the north (east) and also in the south at the inland Sea (Khor Al-Adaid). Zekreet is also a nice drive with isolated beaches.

Best wishes,
An educated Marine Biologist.