Excellent communication and organisation in pick up, at our apartment, for the 40 minute drive to Tigre. (not part of the 8 hours!)
A smallish but comfy boat with very able captain, Thomas. The drive to the fishing ground was longer than expected , but fabulous, speeding, river cruise of 90 minutes to remote and silent river spot. Caught Piranha and catfish -yellow and blue…reasonable size and great fight in them. Delicious breakfast-croissant and ice cold coke and water. Longish-45 minute trip to amazing island-where BBQ and food prepared. We swam and sat and ate salad and beef ribs with company crew-who arrived at island to help with lunch and clean up. Regina, Paul and co. We changed to faster boat for return to Tigre and left the others to clean up. Love that bit! Actually had 9 hours on water. Not as much fishing as we had expected but not a problem because we were totally wowed by the island, fishing spot, and ending up in Uruguay for lunch. 
The weather was very hot so actually we were happy to get to the shaded island and swim.