He bathed in seawater; does that take the place of wudoo’?
Question

                If there is a river or sea near me, and I bathe in it, and after that the time for prayer comes and I do not have any other water apart from that with which I could do wudoo’, is my bathing sufficient to replace wudoo’ and can I pray like that?.
Praise be to Allah.
      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. 

    But if he intended to do both together, and 
    did not start with wudoo’, rather he intended to do ghusl and wudoo’ 
    together with one intention, that is sufficient according to a number of 
    scholars. What is better is to do what the Prophet (blessings and peace of 
    Allah be upon him) did, namely clean oneself and do wudoo’ as for prayer 
    first, then pour water over the body to complete one’s ghusl. This is the 
    Sunnah when purifying oneself from janaabah. This also applies in the case 
    of menses. When a woman’s menses ends, she should clean herself and do wudoo 
    as for prayer, then she should wash herself, making sure that water reaches 
    all parts of the body. This is what is enjoined in sharee‘ah, and this 
    suffices for both wudoo’ and ghusl. 

    The water may come from the sea or a river 
    or a well. Praise be to Allah, the matter is broad in scope. Allah, may He 
    be exalted, said (interpretation of the meaning): “…and you find no 
    water…” [al-Nisa’ 4:43]. 
    Water includes seas, rivers, streams and wells. All of them come under the 
    heading of water. End quote. 

    Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allah 
    have mercy on him)