The BBC News website, BBC Mundo.com and BBCBrasil.com have received well over 1,000 e-mails for Martin Strel as he continues his Amazon swim. Here he answers some more of your questions.
As many of the questions were similar we put the most popular queries to Martin, with the names of those who sent the questions listed underneath.
QUESTIONS AND ANSWERS: 23 MARCH
Q: How are you paying for your trip? Have you got a sponsor?
Gaby Ciacia, England; Moira Harvey, Whitinsville, Massachusetts, US
A: I have sponsors. We couldn't do such a project without sponsors.
We have everything - the boats, food, supplies and so on - for about 70 days. The production cost is about $1m.
Q: How old are you? How long do you intend to continue these challenges?
Aaron, Karachi, Pakistan
A: I am 52. I always say I will continue as long as I stay healthy, and as long as my body still allows me.
I have no limitations. I don't care if I am 62 or 72. I am going to swim for as long as I can.
But I can't tell you if it's going to be two more years or 20 more years.
QUESTIONS AND ANSWERS: 16 MARCH
Q: Which lessons do you think young people can take from your adventure?
Zacarias, Lichinga, Mozambique; Gustavo Manrique Salas, Panama
A: I think they can learn a lot about the Amazon River.
I try to inform the people who live by the river what kind of diseases people can get.
We talk about the cleanliness of the river and the rainforest, and try to make people aware that is a source of our oxygen and to keep it clean.
There is also a message that if you try to reach a goal in your life, you have to go step by step.
My project is very, very long. I planned to do it over many years. I am now doing it over many days.
Like in other things, when you do your job every day, you have to set your goals and never give up. Sometimes people give up too fast and move onto something else, which is not good.
Q: What is your main style of swimming, how many strokes do you do before you put your head in the water again?
Jose Perez, Santiago, Chile
A: I usually swim freestyle. I do about 54 to 56 strokes per minute, this is when I am swimming freestyle and just breathe out of the left and right side.
I'm on my back, usually between 1000 and 1400, when the sun is very strong. I turn on my back and protect my head with a special hat and a mask to protect my face. When I'm on my back I swim mostly with my legs.
Q: What is the most important characteristic a long distance swimmer should have?
Miguel Gonzalez, Dominican Republic
A: The first thing for long distance athletes, not just swimmers, is you have to "grow" in your head, learn how to endure.
Usually, when athletes get to the age of 30, they can only achieve the best results using stamina and endurance. And of course you have to train, and stay concentrated, step by step, keep coming back and never give up.
Q: My son Daniel Sebastian is two years old. Could you give him a message? One day he will understand the significance of what you are doing and I will read this to him.
Julio H Vera, New York, US
A: I would say do sport. Sport is the best thing besides school.
Sport is bringing people together through friendship and collaboration. People who do sport stay very healthy, they live longer than others.
If you look at people who are active and don't smoke or take drugs, they have a good healthy spirit.
QUESTIONS AND ANSWERS: 9 MARCH
Q: Are you aware of the dangers of the cobra sucuri [anaconda]?
Babi, Brasilia, Brazil; Alexandre, Sao Paulo, Brazil; Rufina, Beira, Mozambique; Marcos Melo, Santos, Sao Paulo, Brazil; Emerson Pecly, Rio de Janeiro, Brazil
A: Yes I am. Downstream from Manaus, which we are approaching, there are many animals which could be a danger to me, and of course, kill me.
If some of these animals attack you and you don't have medical help, you can die immediately.
My team knows the Amazon very well, however, and we try to keep swimming in the middle of the river. The rest of the team have already seen many snakes, but we have managed to avoid them.
I have a long boat near me and I swim most of the time at the end of the back of the boat.
I have a guy who is constantly scouting the area where I'll be swimming in the next couple of seconds, so if something happens, he just uses a whistle and stops me and redirects me.
He'll be paying even more attention downstream from Manaus.
Q: What time do you start every day and how many stops do you make?
Joao Alberto Culungo, Cabinda, Angola; Francis, Uberlandia, Minas Gerais, Brazil;Germán, Caracas, Venezuela
A: I start swimming every day about 0715 and finish about 1730.
I stop quite often, about every 30 minutes and drink and talk with my team about how many kms we have covered and what the weather forecast is like.
At lunchtime we stop for about an hour.
I stop more when the sun is strong because I need to drink more. I have got dehydrated a couple of times which is very dangerous.
Q: Do you swim at night?
Wilson Filho, Sao Paulo, Brazil; Valdeci Elias, Paulista, Pernambuco, Brazil
A: Right now we don't swim at night, but later on when we approach the Atlantic Ocean we expect huge tidal changes.
Every six hours the current is going to change, so I may need to swim at night.
That will probably be in the last week.
Q: Is the river more or less polluted in the Brazilian side?
Andres Sayan, Paterson, US
A: I think the river is quite clean overall. Peru was very clean. But in Brazil we haven't approached the big cities yet. Maybe there it will be a little worse.
Every day we see people cleaning their teeth in the river. The river a brown colour but that's because of all the sediment into the water. The water doesn't smell.
Q: Have you seen a lot of devastation of the rainforest?
Adriano Mussolin, Pocos de Caldas, Minas Gerais, Brazil
A: We haven't seen much devastation yet.
I have been in Brazil since 22 February, when we reached Tabatinga.
But we are moving fast. I think the big deforestation areas are still to come.
QUESTIONS AND ANSWERS: 2 MARCH
Q: You mentioned the dangers of the toothpick fish. Have you encountered them or any other dangerous animals that live in the river, such as crocodiles or piranhas?
Eyal Bar-David, Toronto, Canada; Alfred Roberts, Lusaka, Zambia;
Hassan, Melbourne, Australia; Nolen, Leuven, Belgium; Peter Waugh, Liverpool, UK; Siegfried G Mayr, Santiago, Chile; Peter, Attard, Malta; David Pereira, Port of Spain, Trinidad and Tobago
A: We've seen crocodiles on the bank of the river, but thankfully they didn't jump on me. They were either not hungry or they didn't want to attack any humans at that moment.
We are very careful of piranhas. For example, if I get injured and start bleeding, we cover that injured area right away so the blood doesn't attract them.
But there are many other dangerous animals in the river. We saw a huge jellyfish-like creature, like a stingray. They are very dangerous because they have venomous tails. My team managed to distract it as I swam right by it.
We also saw a candiru fish. It was very close to me. About 10 days ago, I came ashore and the local people, who were washing clothes in the river, were shouting: "Hey man, be careful of the candiru!"
It's a very dangerous fish. It's very small, only a couple of centimetres long, and it enters the human body through the nose, mouth, ears, and penis. If you don't have a wet suit, they can get inside you easily, and once they are inside you can't get them out. Like the toothpick fish.
Q: What foods do you eat to keep your strength up?
Amy Hurley, Philadelphia, US; Peter Knight, Helsinki, Finland;
A: I have a really good team. They prepare brilliant food on the boat, not just for me but for the whole team.
Peruvian and Brazilian food are delicious. I have a very big breakfast in the morning, I eat a lot of eggs, ham, cheese, and fruit.
While I'm in the water, I take a couple of minutes break and eat an energy bar or a chocolate bar.
I don't eat much for lunch because if I eat a lot I get sleepy. So I eat a lot in the morning and at night.
Q: What kind of team do you have? Do you have people with various skills such as medical, linguistic, cultural and geographic knowledge? Do they follow you along by boat, or along the side of the river?
Emilie, Colombo, Sri Lanka; Carlos Massanori Morimoto, Londrina, Brazil
A: My team is made up of different technical people who make the swim possible. They are about 20 people in all.
I have river navigators, because I can't really see where I'm going when I'm in the water.
They go ahead of me and see what's coming up. They use satellite navigation and maps and communicate back to the main boat.
We have different types of boats - smaller boats which are constantly near me and a big boat, where the team eats, sleeps and works.
I have pilots and captains to navigate the boats. Then I have a medical team, a film crew that is producing a documentary, an internet crew, photographers, and a writer.
We have a Brazilian guide, Miguel Rocha de Silva, who is famous for guiding Jacques Cousteau on his Amazon expedition 20 years ago.
He has guided many expeditions. He was also with Peter Blake, one of the most famous sailors in the world, who was murdered in 2001 by river pirates near the mouth of the Amazon, in a place called Macapa.
We are not going to Macapa, north of the delta, we are going south to Belem. It's not possible to reach Macapa, as it's too open and the waves are too big.
I expect no problems, because we have great people in our team who know the river.
Q: What do the indigenous people think of your swim?
Thurna Lucero, Isleta Pueblo, New Mexico, US; Cole Farnum, Brownsville, Texas, USA
A: Many of the indigenous people have been really surprised to see me.
There are many tribes along the river. We haven't had a chance to stop and say hello to all of them.
Some of them don't like contact with outsiders. They live as their ancestors did thousands of years ago and no one else can enter into their area.
But some of them are very friendly. The local people prepared a huge ceremony before we left Peru.
I feel like at home generally among the local people here.
What will you do to celebrate once you have finished?
Alex Kruzel, Chicago, Illinois, USA
A: We are going to take a few days off and the whole team will go to a place near the city of Santarem, Brazil.
There is a river there called Tapajos, where you can party day and night, and have fun.
We will stay there for a few days and take some time out for ourselves to celebrate.
Then we will do some TV appearances and interviews.