Marathon Swimming in Vietnam?

Any established routes or good ideas? I went to a study abroad recruiting session at my college yesterday and it put me into south east Asian daydream mode. The likeliness of me actually getting over there is small, but I'd like to know if there's an open water scene there just in case 

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We're all just carbon, water, starlight, oxygen and dreams
http://notdrowningswimming.com - open water adventures of a very ordinary swimmer
Molly Nance, Lincoln, Nebraska
What about something near Hoi An?