Ironically this is his lowball speed given that the upper end of his speed scales to MFTL+ characters because he a fast sea boi.
The Calc[]
The Feat: https://imgur.com/a/gUUuj (The lasers reflect off of his shield and act realistically from what I can see)
Supporting Feats: Reacting to Black Manta's eyebeams.
Measurements:
Aquaman is 6'1, a person is ideally 8 heads tall, meaning his head is 23.1775 cm tall. Assuming the Atlantean shooting at him as a comparably sized head.
Distance arm moved: 201 * 23.1775 / 67 = 69.5325 cm.
296/67
Aquaman's head is 4.417 times smaller than the person shooting.
Angular size is inversely proportional to distance, so Aquaman must be 4.417 head lengths away, or 102.37 cm.
Speed:
(0.695325 m * 2.25E8 m/s) / 1.0237 = 152826145.355 m/s, 0.509 c, Relativistic+.