Materials:
It is better to use cotton yarn. The colour being of your choice. I have brown for the ship, two shades of blue for the waves, and a small amount of white yarn for the sail.
The size of the ship is 5 cm. The bookmark length is 18 cm.
I used mercerized cotton «Pelican», 330 m/ 50 g. I crocheted with 2 strands!
- Crochet hooks in two sizes, I have № 1,25mm и №1,5mm
- Hollow fiber
- A piece of wire approx. 2,0 mm thick and 10 cm long
- A sewing needle
- Transparent glue

Abbreviations:
ch – chain
sl st – slip stitch
sc – single crochet
hdc – half double crochet
inc – increase (2 sc in 1 st)
dec – decrease (single crochet two stitches together)
(...) x N times – repeat instructions in brackets N times

1st part - Deck
Take a smaller crochet hook. I used 1.25
11 ch
1) starting from 2nd ch from hook: inc, 8 sc, in the last stitch: 1 sc, 1 hdc, 1 sc; continue along the other side of chain: 8 sc, inc = 23

2) 2 inc, 9 sc, in 1 loop: 1 sc, 1 hdc, 1 sc; continue: 9 sc, 2 inc = 29 
3) 2 sc, 3 sc in 1 loop, 11 sc, in 1 loop: 1 sc, 1 hdc, 1 sc; continue: 11 sc, 3 sc in 1 loop, 2 sc = 35
4) 3 sc, 3 sc in 1 loop, 13 sc, in 1 loop: 1 sc, 1 hdc, 1 sc; continue: 14 sc, 3 sc in 1 loop, 2 sl st = 41
Fasten off, cut off.
Mark the 37th loop.

2nd part - Ship's hull
Take a larger crochet hook. I used 1.5
10 ch
1) starting from 2nd ch from hook: inc, 7 sc, in the last stitch: 1 sc, 1 hdc, 1 sc; continue along the other side of chain: 7 sc, inc = 21
2) 2 inc, 8 sc, in 1 loop: 1 sc, 1 hdc, 1 sc; continue: 8 sc, 2 inc = 27
3) 2 sc, 3 sc in 1 loop, 10 sc, in 1 loop: 1 sc, 1 hdc, 1 sc; continue: 10 sc, 3 sc in 1 loop, 1 sc, 1 sl st = 33

4) into the back loops only: 16 sc, 2 inc, 14 sc, into the both loops: 1 sc = 35
5) 3 sc, inc, 12 sc, inc, 1 sc, inc, 13 sc, inc, 3 sc =39
6) 19 sc, 3 sc in 1 loop, 19 sc =41
Work 4sc, transfer your PM here.

Fold the wire, as in the photo. The straight part is the mast. The height of the mast must be equal to the length of the deck. Twist the rest of the wire into a spiral.

Apply some transparent glue onto the mast and make neat wraps around it with brown yarn.

Place the spiralled part of the wire onto the bottom of the ship and glue it on. Add some hollow fiber.

Put on the deck, pierce its middle with the mast.

Align the hinges of the deck and the hull. 
7) start from the loop with a marker on:  work 41 sc by hooking through both edges of the parts.

8) 16 sc, 2 inc, 21 sc, 2sl st =43
Fasten off, cut off.

Sail
1) 12 ch, starting from 2nd ch from hook: 11 sc, ch, turn =11
2) 11 sc, ch, turn =11
3) skip 1 loop, 10 sc, ch, turn =10
4) skip 1 loop, 9 sc, ch, turn =9
5-7) 9 sc, ch, turn =9
8) skip 1 loop, 8 sc, ch, turn =8
9) skip 1 loop, 7 sc, ch, turn =7
10-11) 7 sc, ch, turn =7
12) 7 sc
Fasten off, cut off.

Sew the sail at points A and B.

Flag
1) 8 ch, starting from 2nd ch from hook: 7 sc, ch, turn =7
2) 4 sc, 1 sl st, 3 ch, turn =8
3) starting from 2nd ch from hook: 7 sc
Cut off yarn, leave a tail for further operation.

Sew the flag to the mast.

Bookmark - Waves
For waves - two shades of blue. Let's call them both color A and color B.
Start with the colour A. Work 79 ch
1) starting from 2nd ch from hook: inc, (3 sc, 2 dec, 3 sc, 2 inc)х 6 times, 3 sc, dec, ch, turn (78)
2) dec, (3 sc, 2 inc, 3 sc, 2 dec)х 6 times, 3 sc, inc, ch, turn (78)

Change the yarn to colour B.
3) inc, (3 sc, 2 dec, 3 sc, 2 inc)х 6 times, 3 sc, dec, ch, turn (78)
4) dec, (3 sc, 2 inc, 3 sc, 2 dec)х 6 times, 3 sc, inc, ch, turn (78)

Change the yarn to colour A.
5) inc, (3 sc, 2 dec, 3 sc, 2 inc)х 6 times, 3 sc, dec, ch, turn (78)
6) dec, (3 sc, 2 inc, 3 sc, 2 dec)х 6 times, 3 sc, inc (78)
Cut off yarn, leave a tail for further operation.

Sew the "waves" to the bottom of the ship.
The bookmark is completed. Enjoy your reading!