A minor point: since there is usually only one deep end and one shallow end in a pool, they are not often used in superlative form. (Deep end, or deeper end would be common; deepest end is not.)
deep end = bagian dalam
deeper end = bagian yang lebih dalam
deepest end = bagian yang paling dalam
deepest end = bagian yang terdalam
deepest end = bagian terdalam
The deepest part of a swimming pool is generally just referred to as "The deep end".
So this sentence could be translated as either
"They don't dare go to the deep end of the pool."
OR
"They don't dare go to the deepest part of the pool."
The translation is wrong. It should be "They do not dare TO go to the deepest part of the pool" or "They do not dare goING to the deepest part of the pool".