We have about a 99% success rate with spotting crocodiles. The small ones are very reliable but the big ones come and go. Even when they are around they can hold their breath for several hours! Successful spotting depends on many factors, low tide is usually better as there more beaches and less water to hide in.
The weather plays a part, crocs are happy when they are warm so if the water is cold they get out, if the water or the sun is very warm, they stay in but are more active. The Daintree River is a natural wild environment and we cannot guarantee wildlife, but we usually see something interesting and the scenery is always stunning.
The Daintree River is not a zoo and it is illegal to feed the crocodiles so we cannot 100% guarantee we will see one. The most difficult time is in the Summer on a high tide but we can usually find a small one at low tide. If you are unlucky to miss out on a croc, you may come back for a free cruise and try again.
The boat does have a roof but no windows so if it's raining a raincoat would be handy.