There are two fairly obvious overland routes one through the Middle East across Suez and the Levant, and one from Tripoli, via Malta, Sicily, the Strait of Messina to Calabria, the toe of Italy. To get to the south of Spain from either of these two passages would have involved taking the long way round, including the crossing of the Pyrenees in a southerly direction. Several of us have been pursuing the option of the short cut the water traverse from Ceuta to Spain. If people and elephants could get across a wider channel to get to Flores just under a million years ago, I believe it is very likely that the smaller water crossing of the Strait of Gibraltar would have been within human capacity just over a million years ago. Again, floating, rafting on flotsam and possibly even swimming seem to have been early acquisitions in human cultural and behavioural evolution.
Boats are technologically advanced inventions which probably came much later.
These are details. The principle remains that water must have played a crucial role in the distribution of humanity across the planet. The idea was largely ignored by Hardy's contemporaries. Among those who opposed the AAT, some pointed out that there were no fossils to support it. Those fossils already discovered in South and East Africa, four to three million years old, show signs that they belonged to erect bipedal hominids.