Possible Clues:

• Half of 25 across is for snaky type taking time in cool sailing club
• Ship used to clear way in polar waters
• Arctic vessel
• Vehicle with runners and a sail
• Crafty type with reputation for cutting diamonds comes into port
• It may go through the floe
• Vessel cruising over a frozen lake
• Diamond thief initially stole entering Arctic vessel
• One snake seized by bats etc in vessel
• Berg-cracking vessel