Tried it a looong time ago ! 25 yrs next month, wife and I on own built steel
Roberts 38, Trinidad for carnival then over to Guiria to clear customs
, then across gulf to Perdenarles in the north of the delta.From here we only had a road map !We only got to Tucupita as there was a new dam and land reclamation scheme. However an island in the river was the Guirdia post,they had a little ferry
and let us use their dock
[and dinner at the commandants] they said we were the first yacht to visit in many years .We left the boat
there under armed guard, while we rented a car and drove almost to Brazil
,also visiting Angel Falls.On our way back we were able to give photos of themselves to some of the natives we met on the way in. At nights we nosed in to the bank and slept despite the howler monkeys. The rest of this trip should probably have been a book!
It was an amazing episode of our lives,stilt houses, dugout canoes etc to say nothing of being lost
in the jungle for 5 days with gold prospectors and the rental car catching fire.
I would however think that the main channel will have some pretty fierce currents. Good luck, have fun, be adventurous, Bruce.