In the name of Allah, We praise Him, seek His help and ask for His forgiveness. Whoever Allah guides none can misguide, and whoever He allows to fall astray, none can guide them aright.

You have to do wudoo’ using water from whatever is around you of the river or sea. The Prophet (blessings and peace of Allah be upon him) was asked about doing wudoo’ from the sea and he said: “Its water is a means of purification and its dead meat recovered from it is permissible .” So, praise be to Allah, if you took a dip in the sea to cool off or to remove dirt and the like, it is not sufficient; rather you have to do wudoo’.

But if you were in a state of janaabah, and you intended to remove both major and minor impurity by doing ghusl, it is sufficient. However, it is better to do wudoo’ as for prayer, then do ghusl to remove janaabah. This is what the Prophet (blessings and peace of Allah be upon him) used to do. The Prophet (blessings and peace of Allah be upon him) would start with wudoo’. He would clean himself first, then he would do wudoo’ as for prayer, then he would do ghusl. This is the Sunnah and that is sufficient.