import math

def survey_hours(area_w_m, area_h_m, depth_m, speed_kt=3.0,
                 half_angle_deg=60.0, overlap=0.20):
    swath = 2 * depth_m * math.tan(math.radians(half_angle_deg))
    spacing = swath * (1 - overlap)
    lines = math.ceil(area_w_m / spacing)
    line_len = area_h_m
    speed_ms = speed_kt * 0.514
    secs = lines * line_len / speed_ms
    secs += lines * 90       # crude turn penalty
    return secs / 3600.0, lines

print(survey_hours(5000, 3000, 50))   # (~20 h, ~22 lines)
print(survey_hours(2000, 2000, 200))  # deep -> way faster