The list of gifts I found following this White Dot Path with only a few diversion:

E:22 = 1 x 2** Classical Saddle
H:21 = 1 x Lunge
F:19 = 1 x Golden Apple
D:18 = 1 x 2** Classical Saddle
B:18 = 1 x Shower
C:16 = 1 x Golden Apple
D:12 = 1 x 2** Western Saddle Cloth
A:11 = 1 x Croesus' Fortune
F:9 = 1 x Hera's Pack
E:6 = 1 x Philotes' Stroke
B:5 = 1 x 2** Classical Bridle
B:3 = 1 x Golden Apple
D:1 = 500 x Oats
F:4 = 10 x Aging point
I:2 = 1 x Titan's Challenge
J:6 = 1 x Whip
I:8 = 1 x Lunge
M:9 = 1 x 2** Classical Saddle Cloth
O:10 = A horse of the Percheron breed
K:10 = 20 x Leather
J:11 = 1 x Seal of the Apocalypse
F:13 = 6,000 Equus
H:19 = 1 x Helios' Ray
J:22 = 20 x Leather
Q:19 = 1 x Zeus' Lightning Bolt
V:22 = 1 x Philotes' Stroke
V:18 = 1 x 2** Classical Saddle Cloth
P:17 = 1 x Apollo's Lyre
L:16 = 1 x Medusa's Blood
J:13 = 1 x Bell boots
R:15 = 50 x Carrot
V:15 = 1 x Apollo's Lyre
S:12 = 1 x 2** Western Saddle Cloth
Q:13 = A horse of the Percheron breed (just off the White Dot Path)
Q:10 = 1 x Zeus' Lightning Bolt
R:8 = 50 x Carrot
V:6 = 1 x Croesus' Fortune
Q:6 = 10 x Aging point
N:3 = 50 x Carrot
O:1 = 1 x Whip
S:2 = 1 x 2** Classical Bridle
V:3 = 1 x Fertility Wand
A:7 = Hestia's Gift

The final number of passes being based on

How many bones you are finding vs. Relics and other items
How often you can dig (the more relics you find, the better tools you can barter for)

For example - on Preprod, even after using the equivalent of 40 passes, and only missed 10 digs due to a screw-up on my part (I had enough Relics to trade for the next tool as soon as able) - I was STILL short 30 - 40 something bones of the required 162 to get Devoted Indigo.

Here's another rough example of differing amounts of Passes based on 1-day sample results with each tool based on MY experience *you may find more or less bones, relics, traps, prizes, etc*

Snorkel and Mask (10 digs)

8 Relics
2 Bones
0 Prizes
0 Traps

Oxygen Tank (15 digs)

10 Relics
4 Bones
0 Prizes
1 Trap

Diving Suit (20 digs)

10 Relics
6 Bones
2 Prizes
2 Traps

Propeller (25 digs)

13 Relics
8 Bones
2 Prizes
2 Traps

Robot (30 digs)

19 Relics
10 Bones
1 Prizes
0 Traps

Now, let's focus on the Bones gotten. We'll assume with our other digs, we got enough Relics to barter for the better tools for the various amounts of digs per day for these dates *dates are preprod dates NOT live dates*:

Days 1 and 2 (13th and 14th): 10 digs per day
Days 3, 4, and 5 (15th, 16th and 17th): 15 digs per day
Days 6, 7, 8, and 9 (18th, 19th, 20th, and 21st): 20 digs per day
Days 10, 11, 12, and 13 (22nd, 23rd, 24th, and 25th): 25 digs
Days 14, 15, and 16 (26th, 27th, and 28th): 30 digs

So:
Day 1 - 2: 4 Bones
Days 3 - 5: 12 Bones
Days 6 - 9: 24 Bones
Days 10 - 13: 32 Bones
Days 14 - 16: 30 Bones
Final total: 102 Bones
Total needed for Indigo: 162 Bones

*Remember that Mines would need to be used before the promotion ends, so the day 14 - 16 count is not 100% accurate as the 16th is not a full day and you would have to log in before the promotion ends to get your digs in*

Still 60 Bones short of Devoted Indigo - time for Mine usage to make up

Looking at my history with Mine usage in a single day (3 mines for 1 pass):

2 Bones
1 Prize
0 Relics
0 Traps

If I continued to have this luck with single mines...I'm looking at 30 passes to make up my missing 60 Bones (2 bones each time ; 2 x 30 = 60).

If we calculate this with my results based off a run with Double Mines (6 mines for 1 pass):

3 Bones
2 Prizes
1 Relic
0 Traps

This comes out to only needing 20 passes (3 bones each time ; 3 x 20 = 60)

Final potential pass cost based on these numbers: 20 to 30 passes

Again though, this is just based off a very small sample of numbers and the assumption that one will get these amounts every dig.

In short - for the Underwater Excavations - expect it to require anywhere between 10 to 50+ passes.

In the Underwater Excavations
And in the Summer Ride?

This is shire?

Rainbow Divines, Devoted Indigo, Brave Purple, and Secret Rainbow

summer ride promotion (?)