Swimming could do a lot of help to you... --> Swimming could be very helpful... ... some disaster like tsunami. --> ... disasters like tsunamis. or --> ... a disaster like a tsunami. Swimming could be helpful even in a disaster like a tsunami. However, it's an odd statement. In a tsunami, the water current is very strong and swimming is really not helpful at all.

You could write "Swimming could do a lot to help, even in some disaster events such as tsunami.