It is advisable that all foreign tourists visiting Goa that keep their valuables , jewellery , money and passport in lockers provided at the Hotel itself and keep the locker key with them to avoid mishappening.
In case you feel like swimming in the sea when you are at a beach at Goa , keep your belongings safe first also make sure that you are in a safe area of the sea and there are no sharks around , also be careful of High tides and currents which may be hazardous. Some beaches of Goa are dangerous at night because of crabs so be careful and always avoid swimming at night.
It is advisable that you donot accept any eatables from any strangers in Goa because you never know what it contains. Bathing is a part of life in Goa , bathing on beaches with bikinis is not a problem but Bathing without clothes is illegal in Public Beaches of Goa. There are some beaches in goa like the Vagator beach where you can bathe without wearing anything and its legal.