Thanks.
Mild piece of guesswork. Max was born in 1902, so was 12 when his parents were killed. He doesn't look much younger than 12 in this picture, so we are probably talking 1913-14. He is in white with what was in British naval parlance a sennit hat, so we are talking warm weather, though FF is in blues. I imagine the K-u-K Navy had white uniforms for the summer, given that they were mostly in the Adriatic and Mediterranean, but went in and out of them on particular dates rather than according to the weather. I seem to remember that the RAF in Malta in the 1970s went from blue to khaki drill on 1 May and back to blue on 1 October. My guess is a warm day in April, so Max is keeping cool in white, but his father is constrained by dress regulations and must wear blue.
April 1913 is my educated guess, and possibly at Pola.
Ann