what is the name of the first boat that was used in crossing water, when ,who where?

Log. When, who, where,

What water? Crossing a river? A lake? How big does this water have to be?

You do not specify.

It was probably some Viking ship somewhere.

Or caveman Grog threw a log into some water and it floated to the other side of the river.

Thor Heydral wrote about this in ''Early Man And The Ocean'' he experminted with rafts & reed boats & went on archeological digs. Reed boats like they used on the Nile were some of the earliest but probably not the earliest. More likely bamboo or balsa rafts. He speculates that ocean travel was more efficient, easier & faster than traveling over land & that people probably headed out to sea much earlier than most suspect. It is an interesting read - he also wrote Kon Tiki which touches on the same subject.

Our pre-history ancestors were making and using boats.
It is thought that the original settlers of the British Isles may have been fishermen from the area now known as Spain (DNA detective work).
The Vikings were great boating explorers crossing the Atlantic from their Scandinavian origins.

since all boats are used for crossing water, what you want is what was the first boat built.

And that would probably be a log used by some prehistoric guy from 100000 years ago or more. Sorry, l do not know his name, if he had one.

If we just stick with European history (mythology) we can go back a fair way. Jason is ship (Jason and the Argonauts) was called Argo (pre 12th century BC) - so pre 12c BC, Jason (Argo), Mediterranean. From middle eastern tradition you have of course Noah is Ark.
If you mean type of boat (other than raft and dugout) you have coracle.

l think Wylie has the answer.

The boat was in fact a log.

The captain was Og the caveman. Two crew, unnamed.

And the date was four little rocks past the big rock.

This is an easy one. It was made by my great,great, hundreds of great grandpaw cave man dumdum- l was named after him u know. He named his boat ugh!- it was the only word he could say. It happened 237,152 years ago at ugh! lake. A lake that was named by grandpaw dumdum. He needed to get to the other side, because he saw a big ugh! that has just been killed in a fight with another big ugh! & it would supply his family with much needed food.
l got this information from the charcoal drawings on the walls of the family cave. Of course he had a tendency to exaggerate his deeds quite a bit in the drawings, a trait that some in the family say that l have inherited from him, but l strongly disagree with that assessment- l hope that l have helped u somewhat in ur quest for information.
Sincerely, dumdum the 7777th
PS. The boat was only a log, but granpa dumdum greatly exaggerated it is size, I've been told.

This is what is known as ''prehistoric.''

Regards,
Dan