Three years ago we went on a wonderful holiday to South America, the highlight of which was supposed to be a 2-day trip through the Andean lakes by boat and bus from Puerto Varas in Chile to Bariloche (via Puerto Blest). Unfortunately, the weather was appalling with very low cloud throughout and rain most of the time - as a result we saw practically nothing. It was only afterwards we discovered that this weather is the norm (about 250 days a year we were told!). However, we decided that we would like to revisit the Bariloche area and go on a boat trip if, and only if, the weather appeared to give us a much better chance of some views. We were very fortunate that one of the four days that we were staying near Bariloche proved to be one of the best of the year (or so our hotel receptionist told us). Hence we booked a trip from Puerto Panuelo near Llao Llao along the western part of Lago Nahuel Huapi to Puerto Blest, plus an optional add-on of a short cruise on Lago Frias. The good weather and the fact that it was Sunday meant that the boat was pretty crowded, making it advantageous that we had booked a couple of days earlier. The trip to Puerto Blest was magnificent with the sun beating down on the tree-clad mountains fringing the lake, giving many photo opportunities. Before we landed at Puerto Blest (which is basically one hotel and very little else!) we did a detour to disembark for a walk up the impressive Los Cantaros waterfall and to Lago Cantaros with its spectacular reflections. After a short break for refreshment at Puerto Blest Hotel, we were picked up by coach for the short drive to Lago Frias, and the most spectacular views of the snow-covered Cerro Tronador from the tourist boat on the lake. Afterwards, we retraced our steps to Puerto Panuelo, noticing how the colours had changed with the different angle of the sun. By the time we returned to our hotel we had hardly seen a single cloud - we were certainly lucky second time round.
There are just a couple of points to bear in mind - the trip is largely within the national Park and a fee (100 pesos, I believe) is payable before leaving Puerto Panuelo, in addition to the cost of the trip, and it is worth considering taking refreshments with you, as the food on the boat is relatively limited and the time at Puerto Blest is quite short if you are going to Lago Frias.